eric6/Plugins/VcsPlugins/vcsGit/GitLogBrowserDialog.py

# -*- coding: utf-8 -*-

# Copyright (c) 2014 - 2019 Detlev Offenbach <detlev@die-offenbachs.de>
#

"""
Module implementing a dialog to browse the log history.
"""

from __future__ import unicode_literals

import os
import collections

from PyQt5.QtCore import pyqtSlot, Qt, QDate, QProcess, QTimer, QRegExp, \
    QSize, QPoint, QFileInfo
from PyQt5.QtGui import QCursor, QColor, QPixmap, QPainter, QPen, QIcon, \
    QTextCursor
from PyQt5.QtWidgets import QWidget, QDialogButtonBox, QHeaderView, \
    QTreeWidgetItem, QApplication, QLineEdit, QMenu, QInputDialog

from E5Gui.E5Application import e5App
from E5Gui import E5MessageBox, E5FileDialog

from Globals import strToQByteArray

from .Ui_GitLogBrowserDialog import Ui_GitLogBrowserDialog

from .GitDiffHighlighter import GitDiffHighlighter
from .GitDiffGenerator import GitDiffGenerator

import UI.PixmapCache
import Preferences
import Utilities

COLORNAMES = ["red", "green", "purple", "cyan", "olive", "magenta",
              "gray", "yellow", "darkred", "darkgreen", "darkblue",
              "darkcyan", "darkmagenta", "blue"]
COLORS = [str(QColor(x).name()) for x in COLORNAMES]


class GitLogBrowserDialog(QWidget, Ui_GitLogBrowserDialog):
    """
    Class implementing a dialog to browse the log history.
    """
    IconColumn = 0
    CommitIdColumn = 1
    AuthorColumn = 2
    DateColumn = 3
    CommitterColumn = 4
    CommitDateColumn = 5
    SubjectColumn = 6
    BranchColumn = 7
    TagsColumn = 8
    
    def __init__(self, vcs, parent=None):
        """
        Constructor
        
        @param vcs reference to the vcs object
        @param parent parent widget (QWidget)
        """
        super(GitLogBrowserDialog, self).__init__(parent)
        self.setupUi(self)
        
        windowFlags = self.windowFlags()
        windowFlags |= Qt.WindowContextHelpButtonHint
        self.setWindowFlags(windowFlags)
        
        self.mainSplitter.setSizes([300, 400])
        self.mainSplitter.setStretchFactor(0, 1)
        self.mainSplitter.setStretchFactor(1, 2)
        self.diffSplitter.setStretchFactor(0, 1)
        self.diffSplitter.setStretchFactor(1, 2)
        
        self.buttonBox.button(QDialogButtonBox.Close).setEnabled(False)
        self.buttonBox.button(QDialogButtonBox.Cancel).setDefault(True)
        
        self.filesTree.headerItem().setText(self.filesTree.columnCount(), "")
        self.filesTree.header().setSortIndicator(1, Qt.AscendingOrder)
        
        self.upButton.setIcon(UI.PixmapCache.getIcon("1uparrow.png"))
        self.downButton.setIcon(UI.PixmapCache.getIcon("1downarrow.png"))
        
        self.refreshButton = self.buttonBox.addButton(
            self.tr("&Refresh"), QDialogButtonBox.ActionRole)
        self.refreshButton.setToolTip(
            self.tr("Press to refresh the list of commits"))
        self.refreshButton.setEnabled(False)
        
        self.findPrevButton.setIcon(UI.PixmapCache.getIcon("1leftarrow.png"))
        self.findNextButton.setIcon(UI.PixmapCache.getIcon("1rightarrow.png"))
        self.__findBackwards = False
        
        self.modeComboBox.addItem(self.tr("Find"), "find")
        self.modeComboBox.addItem(self.tr("Filter"), "filter")
        
        self.fieldCombo.addItem(self.tr("Commit ID"), "commitId")
        self.fieldCombo.addItem(self.tr("Author"), "author")
        self.fieldCombo.addItem(self.tr("Committer"), "committer")
        self.fieldCombo.addItem(self.tr("Subject"), "subject")
        self.fieldCombo.addItem(self.tr("File"), "file")
        
        self.__logTreeNormalFont = self.logTree.font()
        self.__logTreeNormalFont.setBold(False)
        self.__logTreeBoldFont = self.logTree.font()
        self.__logTreeBoldFont.setBold(True)
        
        font = Preferences.getEditorOtherFonts("MonospacedFont")
        self.diffEdit.setFontFamily(font.family())
        self.diffEdit.setFontPointSize(font.pointSize())
        
        self.diffHighlighter = GitDiffHighlighter(self.diffEdit.document())
        self.__diffGenerator = GitDiffGenerator(vcs, self)
        self.__diffGenerator.finished.connect(self.__generatorFinished)
        
        self.vcs = vcs
        
        self.__detailsTemplate = self.tr(
            "<table>"
            "<tr><td><b>Commit ID</b></td><td>{0}</td></tr>"
            "<tr><td><b>Date</b></td><td>{1}</td></tr>"
            "<tr><td><b>Author</b></td><td>{2} &lt;{3}&gt;</td></tr>"
            "<tr><td><b>Commit Date</b></td><td>{4}</td></tr>"
            "<tr><td><b>Committer</b></td><td>{5} &lt;{6}&gt;</td></tr>"
            "{7}"
            "<tr><td><b>Subject</b></td><td>{8}</td></tr>"
            "{9}"
            "</table>"
        )
        self.__parentsTemplate = self.tr(
            "<tr><td><b>Parents</b></td><td>{0}</td></tr>"
        )
        self.__childrenTemplate = self.tr(
            "<tr><td><b>Children</b></td><td>{0}</td></tr>"
        )
        self.__branchesTemplate = self.tr(
            "<tr><td><b>Branches</b></td><td>{0}</td></tr>"
        )
        self.__tagsTemplate = self.tr(
            "<tr><td><b>Tags</b></td><td>{0}</td></tr>"
        )
        self.__mesageTemplate = self.tr(
            "<tr><td><b>Message</b></td><td>{0}</td></tr>"
        )
        
        self.__formatTemplate = (
            'format:recordstart%n'
            'commit|%h%n'
            'parents|%p%n'
            'author|%an%n'
            'authormail|%ae%n'
            'authordate|%ai%n'
            'committer|%cn%n'
            'committermail|%ce%n'
            'committerdate|%ci%n'
            'refnames|%d%n'
            'subject|%s%n'
            'bodystart%n'
            '%b%n'
            'bodyend%n'
        )
        
        self.__filename = ""
        self.__isFile = False
        self.__selectedCommitIDs = []
        self.intercept = False
        
        self.__initData()
        
        self.fromDate.setDisplayFormat("yyyy-MM-dd")
        self.toDate.setDisplayFormat("yyyy-MM-dd")
        self.__resetUI()
        
        # roles used in the log tree
        self.__subjectRole = Qt.UserRole
        self.__messageRole = Qt.UserRole + 1
        self.__changesRole = Qt.UserRole + 2
        self.__edgesRole = Qt.UserRole + 3
        self.__parentsRole = Qt.UserRole + 4
        self.__branchesRole = Qt.UserRole + 5
        self.__authorMailRole = Qt.UserRole + 6
        self.__committerMailRole = Qt.UserRole + 7
        
        # roles used in the file tree
        self.__diffFileLineRole = Qt.UserRole
        
        self.process = QProcess()
        self.process.finished.connect(self.__procFinished)
        self.process.readyReadStandardOutput.connect(self.__readStdout)
        self.process.readyReadStandardError.connect(self.__readStderr)
        
        self.flags = {
            'A': self.tr('Added'),
            'D': self.tr('Deleted'),
            'M': self.tr('Modified'),
            'C': self.tr('Copied'),
            'R': self.tr('Renamed'),
            'T': self.tr('Type changed'),
            'U': self.tr('Unmerged'),
            'X': self.tr('Unknown'),
        }
        
        self.__dotRadius = 8
        self.__rowHeight = 20
        
        self.logTree.setIconSize(
            QSize(100 * self.__rowHeight, self.__rowHeight))
        
        self.detailsEdit.anchorClicked.connect(self.__commitIdClicked)
        
        self.__initLogTreeContextMenu()
        self.__initActionsMenu()
        
        self.__finishCallbacks = []
    
    def __addFinishCallback(self, callback):
        """
        Private method to add a method to be called once the process finished.
        
        The callback methods are invoke in a FIFO style and are consumed. If
        a callback method needs to be called again, it must be added again.
        
        @param callback callback method
        @type function
        """
        if callback not in self.__finishCallbacks:
            self.__finishCallbacks.append(callback)
    
    def __initLogTreeContextMenu(self):
        """
        Private method to initialize the log tree context menu.
        """
        self.__logTreeMenu = QMenu()
        
        # commit ID column
        act = self.__logTreeMenu.addAction(
            self.tr("Show Commit ID Column"))
        act.setToolTip(self.tr(
            "Press to show the commit ID column"))
        act.setCheckable(True)
        act.setChecked(self.vcs.getPlugin().getPreferences(
            "ShowCommitIdColumn"))
        act.triggered.connect(self.__showCommitIdColumn)
        
        # author and date columns
        act = self.__logTreeMenu.addAction(
            self.tr("Show Author Columns"))
        act.setToolTip(self.tr(
            "Press to show the author columns"))
        act.setCheckable(True)
        act.setChecked(self.vcs.getPlugin().getPreferences(
            "ShowAuthorColumns"))
        act.triggered.connect(self.__showAuthorColumns)
        
        # committer and commit date columns
        act = self.__logTreeMenu.addAction(
            self.tr("Show Committer Columns"))
        act.setToolTip(self.tr(
            "Press to show the committer columns"))
        act.setCheckable(True)
        act.setChecked(self.vcs.getPlugin().getPreferences(
            "ShowCommitterColumns"))
        act.triggered.connect(self.__showCommitterColumns)
        
        # branches column
        act = self.__logTreeMenu.addAction(
            self.tr("Show Branches Column"))
        act.setToolTip(self.tr(
            "Press to show the branches column"))
        act.setCheckable(True)
        act.setChecked(self.vcs.getPlugin().getPreferences(
            "ShowBranchesColumn"))
        act.triggered.connect(self.__showBranchesColumn)
        
        # tags column
        act = self.__logTreeMenu.addAction(
            self.tr("Show Tags Column"))
        act.setToolTip(self.tr(
            "Press to show the Tags column"))
        act.setCheckable(True)
        act.setChecked(self.vcs.getPlugin().getPreferences(
            "ShowTagsColumn"))
        act.triggered.connect(self.__showTagsColumn)
        
        # set column visibility as configured
        self.__showCommitIdColumn(self.vcs.getPlugin().getPreferences(
            "ShowCommitIdColumn"))
        self.__showAuthorColumns(self.vcs.getPlugin().getPreferences(
            "ShowAuthorColumns"))
        self.__showCommitterColumns(self.vcs.getPlugin().getPreferences(
            "ShowCommitterColumns"))
        self.__showBranchesColumn(self.vcs.getPlugin().getPreferences(
            "ShowBranchesColumn"))
        self.__showTagsColumn(self.vcs.getPlugin().getPreferences(
            "ShowTagsColumn"))
    
    def __initActionsMenu(self):
        """
        Private method to initialize the actions menu.
        """
        self.__actionsMenu = QMenu()
        self.__actionsMenu.setTearOffEnabled(True)
        self.__actionsMenu.setToolTipsVisible(True)
        
        self.__cherryAct = self.__actionsMenu.addAction(
            self.tr("Copy Commits"), self.__cherryActTriggered)
        self.__cherryAct.setToolTip(self.tr(
            "Cherry-pick the selected commits to the current branch"))
        
        self.__actionsMenu.addSeparator()
        
        self.__tagAct = self.__actionsMenu.addAction(
            self.tr("Tag"), self.__tagActTriggered)
        self.__tagAct.setToolTip(self.tr("Tag the selected commit"))
        
        self.__branchAct = self.__actionsMenu.addAction(
            self.tr("Branch"), self.__branchActTriggered)
        self.__branchAct.setToolTip(self.tr(
            "Create a new branch at the selected commit."))
        self.__branchSwitchAct = self.__actionsMenu.addAction(
            self.tr("Branch && Switch"), self.__branchSwitchActTriggered)
        self.__branchSwitchAct.setToolTip(self.tr(
            "Create a new branch at the selected commit and switch"
            " the work tree to it."))
        
        self.__switchAct = self.__actionsMenu.addAction(
            self.tr("Switch"), self.__switchActTriggered)
        self.__switchAct.setToolTip(self.tr(
            "Switch the working directory to the selected commit"))
        self.__actionsMenu.addSeparator()
        
        self.__shortlogAct = self.__actionsMenu.addAction(
            self.tr("Show Short Log"), self.__shortlogActTriggered)
        self.__shortlogAct.setToolTip(self.tr(
            "Show a dialog with a log output for release notes"))
        
        self.__describeAct = self.__actionsMenu.addAction(
            self.tr("Describe"), self.__describeActTriggered)
        self.__describeAct.setToolTip(self.tr(
            "Show the most recent tag reachable from a commit"))
        
        self.actionsButton.setIcon(
            UI.PixmapCache.getIcon("actionsToolButton.png"))
        self.actionsButton.setMenu(self.__actionsMenu)
    
    def __initData(self):
        """
        Private method to (re-)initialize some data.
        """
        self.__maxDate = QDate()
        self.__minDate = QDate()
        self.__filterLogsEnabled = True
        
        self.buf = []        # buffer for stdout
        self.diff = None
        self.__started = False
        self.__skipEntries = 0
        self.projectMode = False
        
        # attributes to store log graph data
        self.__commitIds = []
        self.__commitColors = {}
        self.__commitColor = 0
        
        self.__projectRevision = ""
        
        self.__childrenInfo = collections.defaultdict(list)
    
    def closeEvent(self, e):
        """
        Protected slot implementing a close event handler.
        
        @param e close event (QCloseEvent)
        """
        if self.process is not None and \
           self.process.state() != QProcess.NotRunning:
            self.process.terminate()
            QTimer.singleShot(2000, self.process.kill)
            self.process.waitForFinished(3000)
        
        self.vcs.getPlugin().setPreferences(
            "LogBrowserGeometry", self.saveGeometry())
        self.vcs.getPlugin().setPreferences(
            "LogBrowserSplitterStates", [
                self.mainSplitter.saveState(),
                self.detailsSplitter.saveState(),
                self.diffSplitter.saveState(),
            ]
        )
        
        e.accept()
    
    def show(self):
        """
        Public slot to show the dialog.
        """
        self.__reloadGeometry()
        self.__restoreSplitterStates()
        self.__resetUI()
        
        super(GitLogBrowserDialog, self).show()
    
    def __reloadGeometry(self):
        """
        Private method to restore the geometry.
        """
        geom = self.vcs.getPlugin().getPreferences("LogBrowserGeometry")
        if geom.isEmpty():
            s = QSize(1000, 800)
            self.resize(s)
        else:
            self.restoreGeometry(geom)
    
    def __restoreSplitterStates(self):
        """
        Private method to restore the state of the various splitters.
        """
        states = self.vcs.getPlugin().getPreferences(
            "LogBrowserSplitterStates")
        if len(states) == 3:
            # we have three splitters
            self.mainSplitter.restoreState(states[0])
            self.detailsSplitter.restoreState(states[1])
            self.diffSplitter.restoreState(states[2])
    
    def __resetUI(self):
        """
        Private method to reset the user interface.
        """
        self.fromDate.setDate(QDate.currentDate())
        self.toDate.setDate(QDate.currentDate())
        self.fieldCombo.setCurrentIndex(self.fieldCombo.findData("subject"))
        self.limitSpinBox.setValue(self.vcs.getPlugin().getPreferences(
            "LogLimit"))
        self.stopCheckBox.setChecked(self.vcs.getPlugin().getPreferences(
            "StopLogOnCopy"))
        
        self.logTree.clear()
    
    def __resizeColumnsLog(self):
        """
        Private method to resize the log tree columns.
        """
        self.logTree.header().resizeSections(QHeaderView.ResizeToContents)
        self.logTree.header().setStretchLastSection(True)
    
    def __resizeColumnsFiles(self):
        """
        Private method to resize the changed files tree columns.
        """
        self.filesTree.header().resizeSections(QHeaderView.ResizeToContents)
        self.filesTree.header().setStretchLastSection(True)
    
    def __resortFiles(self):
        """
        Private method to resort the changed files tree.
        """
        self.filesTree.setSortingEnabled(True)
        self.filesTree.sortItems(1, Qt.AscendingOrder)
        self.filesTree.setSortingEnabled(False)
    
    def __getColor(self, n):
        """
        Private method to get the (rotating) name of the color given an index.
        
        @param n color index (integer)
        @return color name (string)
        """
        return COLORS[n % len(COLORS)]
    
    def __generateEdges(self, commitId, parents):
        """
        Private method to generate edge info for the give data.
        
        @param commitId commit id to calculate edge info for (string)
        @param parents list of parent commits (list of strings)
        @return tuple containing the column and color index for
            the given node and a list of tuples indicating the edges
            between the given node and its parents
            (integer, integer, [(integer, integer, integer), ...])
        """
        if commitId not in self.__commitIds:
            # new head
            self.__commitIds.append(commitId)
            self.__commitColors[commitId] = self.__commitColor
            self.__commitColor += 1
        
        col = self.__commitIds.index(commitId)
        color = self.__commitColors.pop(commitId)
        nextCommitIds = self.__commitIds[:]
        
        # add parents to next
        addparents = [p for p in parents if p not in nextCommitIds]
        nextCommitIds[col:col + 1] = addparents
        
        # set colors for the parents
        for i, p in enumerate(addparents):
            if not i:
                self.__commitColors[p] = color
            else:
                self.__commitColors[p] = self.__commitColor
                self.__commitColor += 1
        
        # add edges to the graph
        edges = []
        if parents:
            for ecol, ecommitId in enumerate(self.__commitIds):
                if ecommitId in nextCommitIds:
                    edges.append(
                        (ecol, nextCommitIds.index(ecommitId),
                         self.__commitColors[ecommitId]))
                elif ecommitId == commitId:
                    for p in parents:
                        edges.append(
                            (ecol, nextCommitIds.index(p),
                             self.__commitColors[p]))
        
        self.__commitIds = nextCommitIds
        return col, color, edges
    
    def __generateIcon(self, column, color, bottomedges, topedges, dotColor,
                       currentCommit):
        """
        Private method to generate an icon containing the revision tree for the
        given data.
        
        @param column column index of the revision (integer)
        @param color color of the node (integer)
        @param bottomedges list of edges for the bottom of the node
            (list of tuples of three integers)
        @param topedges list of edges for the top of the node
            (list of tuples of three integers)
        @param dotColor color to be used for the dot (QColor)
        @param currentCommit flag indicating to draw the icon for the
            current commit (boolean)
        @return icon for the node (QIcon)
        """
        def col2x(col, radius):
            """
            Local function to calculate a x-position for a column.
            
            @param col column number (integer)
            @param radius radius of the indicator circle (integer)
            """
            return int(1.2 * radius) * col + radius // 2 + 3
        
        radius = self.__dotRadius
        w = len(bottomedges) * radius + 20
        h = self.__rowHeight
        
        dot_x = col2x(column, radius) - radius // 2
        dot_y = h // 2
        
        pix = QPixmap(w, h)
        pix.fill(QColor(0, 0, 0, 0))
        painter = QPainter(pix)
        painter.setRenderHint(QPainter.Antialiasing)
        
        pen = QPen(Qt.blue)
        pen.setWidth(2)
        painter.setPen(pen)
        
        lpen = QPen(pen)
        lpen.setColor(Qt.black)
        painter.setPen(lpen)
        
        # draw the revision history lines
        for y1, y2, lines in ((0, h, bottomedges),
                              (-h, 0, topedges)):
            if lines:
                for start, end, ecolor in lines:
                    lpen = QPen(pen)
                    lpen.setColor(QColor(self.__getColor(ecolor)))
                    lpen.setWidth(2)
                    painter.setPen(lpen)
                    x1 = col2x(start, radius)
                    x2 = col2x(end, radius)
                    painter.drawLine(x1, dot_y + y1, x2, dot_y + y2)
        
        penradius = 1
        pencolor = Qt.black
        
        dot_y = (h // 2) - radius // 2
        
        # draw a dot for the revision
        if currentCommit:
            # enlarge dot for the current revision
            delta = 2
            radius += 2 * delta
            dot_y -= delta
            dot_x -= delta
        painter.setBrush(dotColor)
        pen = QPen(pencolor)
        pen.setWidth(penradius)
        painter.setPen(pen)
        painter.drawEllipse(dot_x, dot_y, radius, radius)
        painter.end()
        return QIcon(pix)
    
    def __identifyProject(self):
        """
        Private method to determine the revision of the project directory.
        """
        errMsg = ""
        
        args = self.vcs.initCommand("show")
        args.append("--abbrev={0}".format(
            self.vcs.getPlugin().getPreferences("CommitIdLength")))
        args.append("--format=%h")
        args.append("--no-patch")
        args.append("HEAD")
        
        output = ""
        process = QProcess()
        process.setWorkingDirectory(self.repodir)
        process.start('git', args)
        procStarted = process.waitForStarted(5000)
        if procStarted:
            finished = process.waitForFinished(30000)
            if finished and process.exitCode() == 0:
                output = str(process.readAllStandardOutput(),
                             Preferences.getSystem("IOEncoding"),
                             'replace')
            else:
                if not finished:
                    errMsg = self.tr(
                        "The git process did not finish within 30s.")
        else:
            errMsg = self.tr("Could not start the git executable.")
        
        if errMsg:
            E5MessageBox.critical(
                self,
                self.tr("Git Error"),
                errMsg)
        
        if output:
            self.__projectRevision = output.strip()
    
    def __generateLogItem(self, author, date, committer, commitDate, subject,
                          message, commitId, changedPaths, parents, refnames,
                          authorMail, committerMail):
        """
        Private method to generate a log tree entry.
        
        @param author author info (string)
        @param date date info (string)
        @param committer committer info (string)
        @param commitDate commit date info (string)
        @param subject subject of the log entry (string)
        @param message text of the log message (list of strings)
        @param commitId commit id info (string)
        @param changedPaths list of dictionary objects containing
            info about the changed files/directories
        @param parents list of parent revisions (list of integers)
        @param refnames tags and branches of the commit (string)
        @param authorMail author's email address (string)
        @param committerMail committer's email address (string)
        @return reference to the generated item (QTreeWidgetItem)
        """
        branches = []
        allBranches = []
        tags = []
        names = refnames.strip()[1:-1].split(",")
        for name in names:
            name = name.strip()
            if name:
                if "HEAD" in name:
                    tags.append(name)
                elif name.startswith("tag: "):
                    tags.append(name.split()[1])
                else:
                    if "/" not in name:
                        branches.append(name)
                    elif "refs/bisect/" in name:
                        bname = name.replace("refs/", "").split("-", 1)[0]
                        branches.append(bname)
                    else:
                        branches.append(name)
                    allBranches.append(name)
        
        logMessageColumnWidth = self.vcs.getPlugin().getPreferences(
            "LogSubjectColumnWidth")
        msgtxt = subject
        if logMessageColumnWidth and len(msgtxt) > logMessageColumnWidth:
            msgtxt = "{0}...".format(msgtxt[:logMessageColumnWidth])
        columnLabels = [
            "",
            commitId,
            author,
            date.rsplit(None, 1)[0].rsplit(":", 1)[0],
            committer,
            commitDate.rsplit(None, 1)[0].rsplit(":", 1)[0],
            msgtxt,
            ", ".join(branches),
            ", ".join(tags),
        ]
        itm = QTreeWidgetItem(self.logTree, columnLabels)
        
        parents = [p.strip() for p in parents.split()]
        column, color, edges = self.__generateEdges(commitId, parents)
        
        itm.setData(0, self.__subjectRole, subject)
        itm.setData(0, self.__messageRole, message)
        itm.setData(0, self.__changesRole, changedPaths)
        itm.setData(0, self.__edgesRole, edges)
        itm.setData(0, self.__branchesRole, allBranches)
        itm.setData(0, self.__authorMailRole, authorMail)
        itm.setData(0, self.__committerMailRole, committerMail)
        if not parents:
            itm.setData(0, self.__parentsRole, [])
        else:
            itm.setData(0, self.__parentsRole, parents)
            for parent in parents:
                self.__childrenInfo[parent].append(commitId)
        
        if self.logTree.topLevelItemCount() > 1:
            topedges = \
                self.logTree.topLevelItem(
                    self.logTree.indexOfTopLevelItem(itm) - 1)\
                .data(0, self.__edgesRole)
        else:
            topedges = None
        
        icon = self.__generateIcon(column, color, edges, topedges,
                                   QColor("blue"),
                                   commitId == self.__projectRevision)
        itm.setIcon(0, icon)
        
        return itm
    
    def __generateFileItem(self, action, path, copyfrom, additions, deletions):
        """
        Private method to generate a changed files tree entry.
        
        @param action indicator for the change action ("A", "C", "D", "M",
            "R", "T", "U", "X")
        @param path path of the file in the repository (string)
        @param copyfrom path the file was copied from (string)
        @param additions number of added lines (int)
        @param deletions number of deleted lines (int)
        @return reference to the generated item (QTreeWidgetItem)
        """
        if len(action) > 1:
            # includes confidence level
            confidence = int(action[1:])
            actionTxt = self.tr("{0} ({1}%)", "action, confidence").format(
                self.flags[action[0]], confidence)
        else:
            actionTxt = self.flags[action]
        itm = QTreeWidgetItem(self.filesTree, [
            actionTxt,
            path,
            str(additions),
            str(deletions),
            copyfrom,
        ])
        
        itm.setTextAlignment(2, Qt.AlignRight)
        itm.setTextAlignment(3, Qt.AlignRight)
        
        return itm
    
    def __getLogEntries(self, skip=0, noEntries=0):
        """
        Private method to retrieve log entries from the repository.
        
        @param skip number of log entries to skip (integer)
        @keyparam noEntries number of entries to get (0 = default) (int)
        """
        self.buttonBox.button(QDialogButtonBox.Close).setEnabled(False)
        self.buttonBox.button(QDialogButtonBox.Cancel).setEnabled(True)
        self.buttonBox.button(QDialogButtonBox.Cancel).setDefault(True)
        QApplication.processEvents()
        
        QApplication.setOverrideCursor(QCursor(Qt.WaitCursor))
        QApplication.processEvents()
        
        self.buf = []
        self.cancelled = False
        self.errors.clear()
        self.intercept = False
        
        if noEntries == 0:
            noEntries = self.limitSpinBox.value()
        
        args = self.vcs.initCommand("log")
        args.append('--max-count={0}'.format(noEntries))
        args.append('--numstat')
        args.append('--abbrev={0}'.format(
            self.vcs.getPlugin().getPreferences("CommitIdLength")))
        if self.vcs.getPlugin().getPreferences("FindCopiesHarder"):
            args.append('--find-copies-harder')
        args.append('--format={0}'.format(self.__formatTemplate))
        args.append('--full-history')
        args.append('--all')
        args.append('--skip={0}'.format(skip))
        if not self.projectMode:
            if not self.stopCheckBox.isChecked():
                args.append('--follow')
            args.append('--')
            args.append(self.__filename)
        
        self.process.kill()
        
        self.process.setWorkingDirectory(self.repodir)
        
        self.process.start('git', args)
        procStarted = self.process.waitForStarted(5000)
        if not procStarted:
            self.inputGroup.setEnabled(False)
            self.inputGroup.hide()
            E5MessageBox.critical(
                self,
                self.tr('Process Generation Error'),
                self.tr(
                    'The process {0} could not be started. '
                    'Ensure, that it is in the search path.'
                ).format('git'))
    
    def start(self, fn, isFile=False, noEntries=0):
        """
        Public slot to start the git log command.
        
        @param fn filename to show the log for (string)
        @keyparam isFile flag indicating log for a file is to be shown
            (boolean)
        @keyparam noEntries number of entries to get (0 = default) (int)
        """
        self.__isFile = isFile
        
        self.sbsSelectLabel.clear()
        
        self.errorGroup.hide()
        QApplication.processEvents()
        
        self.__initData()
        
        self.__filename = fn
        self.dname, self.fname = self.vcs.splitPath(fn)
        
        # find the root of the repo
        self.repodir = self.dname
        while not os.path.isdir(os.path.join(self.repodir, self.vcs.adminDir)):
            self.repodir = os.path.dirname(self.repodir)
            if os.path.splitdrive(self.repodir)[1] == os.sep:
                return
        
        self.projectMode = (self.fname == "." and self.dname == self.repodir)
        self.stopCheckBox.setDisabled(self.projectMode or self.fname == ".")
        self.activateWindow()
        self.raise_()
        
        self.logTree.clear()
        self.__started = True
        self.__identifyProject()
        self.__getLogEntries(noEntries=noEntries)
    
    def __procFinished(self, exitCode, exitStatus):
        """
        Private slot connected to the finished signal.
        
        @param exitCode exit code of the process (integer)
        @param exitStatus exit status of the process (QProcess.ExitStatus)
        """
        self.__processBuffer()
        self.__finish()
    
    def __finish(self):
        """
        Private slot called when the process finished or the user pressed
        the button.
        """
        if self.process is not None and \
           self.process.state() != QProcess.NotRunning:
            self.process.terminate()
            QTimer.singleShot(2000, self.process.kill)
            self.process.waitForFinished(3000)
        
        QApplication.restoreOverrideCursor()
        
        self.buttonBox.button(QDialogButtonBox.Close).setEnabled(True)
        self.buttonBox.button(QDialogButtonBox.Cancel).setEnabled(False)
        self.buttonBox.button(QDialogButtonBox.Close).setDefault(True)
        
        self.inputGroup.setEnabled(False)
        self.inputGroup.hide()
        self.refreshButton.setEnabled(True)
        
        while self.__finishCallbacks:
            self.__finishCallbacks.pop(0)()
    
    def __processBufferItem(self, logEntry):
        """
        Private method to process a log entry.
        
        @param logEntry dictionary as generated by __processBuffer
        """
        self.__generateLogItem(
            logEntry["author"], logEntry["authordate"],
            logEntry["committer"], logEntry["committerdate"],
            logEntry["subject"], logEntry["body"],
            logEntry["commit"], logEntry["changed_files"],
            logEntry["parents"], logEntry["refnames"],
            logEntry["authormail"], logEntry["committermail"]
        )
        for date in [logEntry["authordate"], logEntry["committerdate"]]:
            dt = QDate.fromString(date, Qt.ISODate)
            if not self.__maxDate.isValid() and \
               not self.__minDate.isValid():
                self.__maxDate = dt
                self.__minDate = dt
            else:
                if self.__maxDate < dt:
                    self.__maxDate = dt
                if self.__minDate > dt:
                    self.__minDate = dt
    
    def __processBuffer(self):
        """
        Private method to process the buffered output of the git log command.
        """
        noEntries = 0
        logEntry = {"changed_files": []}
        descriptionBody = False
        
        for line in self.buf:
            line = line.rstrip()
            if line == "recordstart":
                if len(logEntry) > 1:
                    self.__processBufferItem(logEntry)
                    noEntries += 1
                logEntry = {"changed_files": []}
                descriptionBody = False
                fileChanges = False
                body = []
            elif line == "bodystart":
                descriptionBody = True
            elif line == "bodyend":
                if bool(body) and not bool(body[-1]):
                    body.pop()
                logEntry["body"] = body
                descriptionBody = False
                fileChanges = True
            elif descriptionBody:
                body.append(line)
            elif fileChanges:
                if line:
                    if "changed_files" not in logEntry:
                        logEntry["changed_files"] = []
                    changeInfo = line.strip().split("\t")
                    if "=>" in changeInfo[2]:
                        # copy/move
                        if "{" in changeInfo[2] and "}" in changeInfo[2]:
                            # change info of the form
                            # test/{pack1 => pack2}/file1.py
                            head, tail = changeInfo[2].split("{", 1)
                            middle, tail = tail.split("}", 1)
                            middleSrc, middleDst = middle.split("=>")
                            src = head + middleSrc.strip() + tail
                            dst = head + middleDst.strip() + tail
                        else:
                            src, dst = changeInfo[2].split("=>")
                        logEntry["changed_files"].append({
                            "action": "C",
                            "added": changeInfo[0].strip(),
                            "deleted": changeInfo[1].strip(),
                            "path": dst.strip(),
                            "copyfrom": src.strip(),
                        })
                    else:
                        logEntry["changed_files"].append({
                            "action": "M",
                            "added": changeInfo[0].strip(),
                            "deleted": changeInfo[1].strip(),
                            "path": changeInfo[2].strip(),
                            "copyfrom": "",
                        })
            else:
                try:
                    key, value = line.split("|", 1)
                except ValueError:
                    key = ""
                    value = line
                if key in ("commit", "parents", "author", "authormail",
                           "authordate", "committer", "committermail",
                           "committerdate", "refnames", "subject"):
                    logEntry[key] = value.strip()
        if len(logEntry) > 1:
            self.__processBufferItem(logEntry)
            noEntries += 1
        
        self.__resizeColumnsLog()
        
        if self.__started:
            if self.__selectedCommitIDs:
                self.logTree.setCurrentItem(self.logTree.findItems(
                    self.__selectedCommitIDs[0], Qt.MatchExactly,
                    self.CommitIdColumn)[0])
            else:
                self.logTree.setCurrentItem(self.logTree.topLevelItem(0))
            self.__started = False
        
        self.__skipEntries += noEntries
        if noEntries < self.limitSpinBox.value() and not self.cancelled:
            self.nextButton.setEnabled(False)
            self.limitSpinBox.setEnabled(False)
        else:
            self.nextButton.setEnabled(True)
            self.limitSpinBox.setEnabled(True)
        
        # update the log filters
        self.__filterLogsEnabled = False
        self.fromDate.setMinimumDate(self.__minDate)
        self.fromDate.setMaximumDate(self.__maxDate)
        self.fromDate.setDate(self.__minDate)
        self.toDate.setMinimumDate(self.__minDate)
        self.toDate.setMaximumDate(self.__maxDate)
        self.toDate.setDate(self.__maxDate)
        
        self.__filterLogsEnabled = True
        if self.__actionMode() == "filter":
            self.__filterLogs()
        
        self.__updateToolMenuActions()
        
        # restore selected items
        if self.__selectedCommitIDs:
            for commitID in self.__selectedCommitIDs:
                items = self.logTree.findItems(
                    commitID, Qt.MatchExactly, self.CommitIdColumn)
                if items:
                    items[0].setSelected(True)
            self.__selectedCommitIDs = []
    
    def __readStdout(self):
        """
        Private slot to handle the readyReadStandardOutput signal.
        
        It reads the output of the process and inserts it into a buffer.
        """
        self.process.setReadChannel(QProcess.StandardOutput)
        
        while self.process.canReadLine():
            line = str(self.process.readLine(),
                       Preferences.getSystem("IOEncoding"),
                       'replace')
            self.buf.append(line)
    
    def __readStderr(self):
        """
        Private slot to handle the readyReadStandardError signal.
        
        It reads the error output of the process and inserts it into the
        error pane.
        """
        if self.process is not None:
            s = str(self.process.readAllStandardError(),
                    Preferences.getSystem("IOEncoding"),
                    'replace')
            self.__showError(s)
    
    def __showError(self, out):
        """
        Private slot to show some error.
        
        @param out error to be shown (string)
        """
        self.errorGroup.show()
        self.errors.insertPlainText(out)
        self.errors.ensureCursorVisible()
        
        # show input in case the process asked for some input
        self.inputGroup.setEnabled(True)
        self.inputGroup.show()
    
    def on_buttonBox_clicked(self, button):
        """
        Private slot called by a button of the button box clicked.
        
        @param button button that was clicked (QAbstractButton)
        """
        if button == self.buttonBox.button(QDialogButtonBox.Close):
            self.close()
        elif button == self.buttonBox.button(QDialogButtonBox.Cancel):
            self.cancelled = True
            self.__finish()
        elif button == self.refreshButton:
            self.on_refreshButton_clicked()
    
    @pyqtSlot()
    def on_refreshButton_clicked(self):
        """
        Private slot to refresh the log.
        """
        self.buttonBox.button(QDialogButtonBox.Close).setEnabled(False)
        self.buttonBox.button(QDialogButtonBox.Cancel).setEnabled(True)
        self.buttonBox.button(QDialogButtonBox.Cancel).setDefault(True)
        
        self.refreshButton.setEnabled(False)
        
        # save the selected items commit IDs
        self.__selectedCommitIDs = []
        for item in self.logTree.selectedItems():
            self.__selectedCommitIDs.append(item.text(self.CommitIdColumn))
        
        self.start(self.__filename, isFile=self.__isFile,
                   noEntries=self.logTree.topLevelItemCount())
    
    def on_passwordCheckBox_toggled(self, isOn):
        """
        Private slot to handle the password checkbox toggled.
        
        @param isOn flag indicating the status of the check box (boolean)
        """
        if isOn:
            self.input.setEchoMode(QLineEdit.Password)
        else:
            self.input.setEchoMode(QLineEdit.Normal)
    
    @pyqtSlot()
    def on_sendButton_clicked(self):
        """
        Private slot to send the input to the git process.
        """
        inputTxt = self.input.text()
        inputTxt += os.linesep
        
        if self.passwordCheckBox.isChecked():
            self.errors.insertPlainText(os.linesep)
            self.errors.ensureCursorVisible()
        else:
            self.errors.insertPlainText(inputTxt)
            self.errors.ensureCursorVisible()
        self.errorGroup.show()
        
        self.process.write(strToQByteArray(inputTxt))
        
        self.passwordCheckBox.setChecked(False)
        self.input.clear()
    
    def on_input_returnPressed(self):
        """
        Private slot to handle the press of the return key in the input field.
        """
        self.intercept = True
        self.on_sendButton_clicked()
    
    def keyPressEvent(self, evt):
        """
        Protected slot to handle a key press event.
        
        @param evt the key press event (QKeyEvent)
        """
        if self.intercept:
            self.intercept = False
            evt.accept()
            return
        super(GitLogBrowserDialog, self).keyPressEvent(evt)
    
    def __prepareFieldSearch(self):
        """
        Private slot to prepare the filed search data.
        
        @return tuple of field index, search expression and flag indicating
            that the field index is a data role (integer, string, boolean)
        """
        indexIsRole = False
        txt = self.fieldCombo.itemData(self.fieldCombo.currentIndex())
        if txt == "author":
            fieldIndex = self.AuthorColumn
            searchRx = QRegExp(self.rxEdit.text(), Qt.CaseInsensitive)
        elif txt == "committer":
            fieldIndex = self.CommitterColumn
            searchRx = QRegExp(self.rxEdit.text(), Qt.CaseInsensitive)
        elif txt == "commitId":
            fieldIndex = self.CommitIdColumn
            txt = self.rxEdit.text()
            if txt.startswith("^"):
                searchRx = QRegExp(r"^\s*{0}".format(txt[1:]),
                                   Qt.CaseInsensitive)
            else:
                searchRx = QRegExp(txt, Qt.CaseInsensitive)
        elif txt == "file":
            fieldIndex = self.__changesRole
            searchRx = QRegExp(self.rxEdit.text(), Qt.CaseInsensitive)
            indexIsRole = True
        else:
            fieldIndex = self.__subjectRole
            searchRx = QRegExp(self.rxEdit.text(), Qt.CaseInsensitive)
            indexIsRole = True
        
        return fieldIndex, searchRx, indexIsRole
    
    def __filterLogs(self):
        """
        Private method to filter the log entries.
        """
        if self.__filterLogsEnabled:
            from_ = self.fromDate.date().toString("yyyy-MM-dd")
            to_ = self.toDate.date().addDays(1).toString("yyyy-MM-dd")
            fieldIndex, searchRx, indexIsRole = self.__prepareFieldSearch()
            
            visibleItemCount = self.logTree.topLevelItemCount()
            currentItem = self.logTree.currentItem()
            for topIndex in range(self.logTree.topLevelItemCount()):
                topItem = self.logTree.topLevelItem(topIndex)
                if indexIsRole:
                    if fieldIndex == self.__changesRole:
                        changes = topItem.data(0, self.__changesRole)
                        txt = "\n".join(
                            [c["path"] for c in changes] +
                            [c["copyfrom"] for c in changes]
                        )
                    else:
                        # Filter based on complete subject text
                        txt = topItem.data(0, self.__subjectRole)
                else:
                    txt = topItem.text(fieldIndex)
                if topItem.text(self.DateColumn) <= to_ and \
                   topItem.text(self.DateColumn) >= from_ and \
                   searchRx.indexIn(txt) > -1:
                    topItem.setHidden(False)
                    if topItem is currentItem:
                        self.on_logTree_currentItemChanged(topItem, None)
                else:
                    topItem.setHidden(True)
                    if topItem is currentItem:
                        self.filesTree.clear()
                    visibleItemCount -= 1
            self.logTree.header().setSectionHidden(
                self.IconColumn,
                visibleItemCount != self.logTree.topLevelItemCount())
    
    def __updateSbsSelectLabel(self):
        """
        Private slot to update the enabled status of the diff buttons.
        """
        self.sbsSelectLabel.clear()
        if self.__isFile:
            selectedItems = self.logTree.selectedItems()
            if len(selectedItems) == 1:
                currentItem = selectedItems[0]
                commit2 = currentItem.text(self.CommitIdColumn).strip()
                parents = currentItem.data(0, self.__parentsRole)
                if parents:
                    parentLinks = []
                    for index in range(len(parents)):
                        parentLinks.append(
                            '<a href="sbsdiff:{0}_{1}">&nbsp;{2}&nbsp;</a>'
                            .format(parents[index], commit2, index + 1))
                    self.sbsSelectLabel.setText(
                        self.tr('Side-by-Side Diff to Parent {0}').format(
                            " ".join(parentLinks)))
            elif len(selectedItems) == 2:
                commit2 = selectedItems[0].text(self.CommitIdColumn)
                commit1 = selectedItems[1].text(self.CommitIdColumn)
                index2 = self.logTree.indexOfTopLevelItem(selectedItems[0])
                index1 = self.logTree.indexOfTopLevelItem(selectedItems[1])
                
                if index2 < index1:
                    # swap to always compare old to new
                    commit1, commit2 = commit2, commit1
                self.sbsSelectLabel.setText(self.tr(
                    '<a href="sbsdiff:{0}_{1}">Side-by-Side Compare</a>')
                    .format(commit1, commit2))
    
    def __updateToolMenuActions(self):
        """
        Private slot to update the status of the tool menu actions and
        the tool menu button.
        """
        if self.projectMode:
            selectCount = len(self.logTree.selectedItems())
            self.__cherryAct.setEnabled(selectCount > 0)
            self.__describeAct.setEnabled(selectCount > 0)
            self.__tagAct.setEnabled(selectCount == 1)
            self.__switchAct.setEnabled(selectCount == 1)
            self.__branchAct.setEnabled(selectCount == 1)
            self.__branchSwitchAct.setEnabled(selectCount == 1)
            self.__shortlogAct.setEnabled(selectCount == 1)
            
            self.actionsButton.setEnabled(True)
        else:
            self.actionsButton.setEnabled(False)
    
    def __updateDetailsAndFiles(self):
        """
        Private slot to update the details and file changes panes.
        """
        self.detailsEdit.clear()
        self.filesTree.clear()
        self.__diffUpdatesFiles = False
        
        selectedItems = self.logTree.selectedItems()
        if len(selectedItems) == 1:
            self.detailsEdit.setHtml(
                self.__generateDetailsTableText(selectedItems[0]))
            self.__updateFilesTree(self.filesTree, selectedItems[0])
            self.__resizeColumnsFiles()
            self.__resortFiles()
            if self.filesTree.topLevelItemCount() == 0:
                self.__diffUpdatesFiles = True
                # give diff a chance to update the files list
        elif len(selectedItems) == 2:
            self.__diffUpdatesFiles = True
            index1 = self.logTree.indexOfTopLevelItem(selectedItems[0])
            index2 = self.logTree.indexOfTopLevelItem(selectedItems[1])
            if index1 > index2:
                # Swap the entries
                selectedItems[0], selectedItems[1] = \
                    selectedItems[1], selectedItems[0]
            html = "{0}<hr/>{1}".format(
                self.__generateDetailsTableText(selectedItems[0]),
                self.__generateDetailsTableText(selectedItems[1]),
            )
            self.detailsEdit.setHtml(html)
            # self.filesTree is updated by the diff
    
    def __generateDetailsTableText(self, itm):
        """
        Private method to generate an HTML table with the details of the given
        changeset.
        
        @param itm reference to the item the table should be based on
        @type QTreeWidgetItem
        @return HTML table containing details
        @rtype str
        """
        if itm is not None:
            commitId = itm.text(self.CommitIdColumn)
            
            parentLinks = []
            for parent in [str(x) for x in itm.data(0, self.__parentsRole)]:
                parentLinks.append('<a href="rev:{0}">{0}</a>'.format(parent))
            if parentLinks:
                parentsStr = self.__parentsTemplate.format(
                    ", ".join(parentLinks))
            else:
                parentsStr = ""
            
            childLinks = []
            for child in [str(x) for x in self.__childrenInfo[commitId]]:
                childLinks.append('<a href="rev:{0}">{0}</a>'.format(child))
            if childLinks:
                childrenStr = self.__childrenTemplate.format(
                    ", ".join(childLinks))
            else:
                childrenStr = ""
            
            branchLinks = []
            for branch, branchHead in self.__getBranchesForCommit(commitId):
                branchLinks.append('<a href="rev:{0}">{1}</a>'.format(
                    branchHead, branch))
            if branchLinks:
                branchesStr = self.__branchesTemplate.format(
                    ", ".join(branchLinks))
            else:
                branchesStr = ""
            
            tagLinks = []
            for tag, tagCommit in self.__getTagsForCommit(commitId):
                if tagCommit:
                    tagLinks.append('<a href="rev:{0}">{1}</a>'.format(
                        tagCommit, tag))
                else:
                    tagLinks.append(tag)
            if tagLinks:
                tagsStr = self.__tagsTemplate.format(
                    ", ".join(tagLinks))
            else:
                tagsStr = ""
            
            if itm.data(0, self.__messageRole):
                messageStr = self.__mesageTemplate.format(
                    "<br/>".join(itm.data(0, self.__messageRole)))
            else:
                messageStr = ""
            
            html = self.__detailsTemplate.format(
                commitId,
                itm.text(self.DateColumn),
                itm.text(self.AuthorColumn),
                itm.data(0, self.__authorMailRole).strip(),
                itm.text(self.CommitDateColumn),
                itm.text(self.CommitterColumn),
                itm.data(0, self.__committerMailRole).strip(),
                parentsStr + childrenStr + branchesStr + tagsStr,
                itm.data(0, self.__subjectRole),
                messageStr,
            )
        else:
            html = ""
        
        return html
    
    def __updateFilesTree(self, parent, itm):
        """
        Private method to update the files tree with changes of the given item.
        
        @param parent parent for the items to be added
        @type QTreeWidget or QTreeWidgetItem
        @param itm reference to the item the update should be based on
        @type QTreeWidgetItem
        """
        if itm is not None:
            changes = itm.data(0, self.__changesRole)
            if len(changes) > 0:
                for change in changes:
                    self.__generateFileItem(
                        change["action"], change["path"], change["copyfrom"],
                        change["added"], change["deleted"])
                self.__resizeColumnsFiles()
                self.__resortFiles()
    
    def __getBranchesForCommit(self, commitId):
        """
        Private method to get all branches reachable from a commit ID.
        
        @param commitId commit ID to get the branches for
        @type str
        @return list of tuples containing the branch name and the associated
            commit ID of its branch head
        @rtype tuple of (str, str)
        """
        branches = []
        
        args = self.vcs.initCommand("branch")
        args.append("--list")
        args.append("--verbose")
        args.append("--contains")
        args.append(commitId)
        
        output = ""
        process = QProcess()
        process.setWorkingDirectory(self.repodir)
        process.start('git', args)
        procStarted = process.waitForStarted(5000)
        if procStarted:
            finished = process.waitForFinished(30000)
            if finished and process.exitCode() == 0:
                output = str(process.readAllStandardOutput(),
                             Preferences.getSystem("IOEncoding"),
                             'replace')
        
        if output:
            for line in output.splitlines():
                name, commitId = line[2:].split(None, 2)[:2]
                branches.append((name, commitId))
        
        return branches
    
    def __getTagsForCommit(self, commitId):
        """
        Private method to get all tags reachable from a commit ID.
        
        @param commitId commit ID to get the tags for
        @type str
        @return list of tuples containing the tag name and the associated
            commit ID
        @rtype tuple of (str, str)
        """
        tags = []
        
        args = self.vcs.initCommand("tag")
        args.append("--list")
        args.append("--contains")
        args.append(commitId)
        
        output = ""
        process = QProcess()
        process.setWorkingDirectory(self.repodir)
        process.start('git', args)
        procStarted = process.waitForStarted(5000)
        if procStarted:
            finished = process.waitForFinished(30000)
            if finished and process.exitCode() == 0:
                output = str(process.readAllStandardOutput(),
                             Preferences.getSystem("IOEncoding"),
                             'replace')
        
        if output:
            tagNames = []
            for line in output.splitlines():
                tagNames.append(line.strip())
            
            # determine the commit IDs for the tags
            for tagName in tagNames:
                commitId = self.__getCommitForTag(tagName)
                tags.append((tagName, commitId))
        
        return tags
    
    def __getCommitForTag(self, tag):
        """
        Private method to get the commit id for a tag.
        
        @param tag tag name (string)
        @return commit id shortened to 10 characters (string)
        """
        args = self.vcs.initCommand("show")
        args.append("--abbrev-commit")
        args.append("--abbrev={0}".format(
            self.vcs.getPlugin().getPreferences("CommitIdLength")))
        args.append("--no-patch")
        args.append(tag)
        
        output = ""
        process = QProcess()
        process.setWorkingDirectory(self.repodir)
        process.start('git', args)
        procStarted = process.waitForStarted(5000)
        if procStarted:
            finished = process.waitForFinished(30000)
            if finished and process.exitCode() == 0:
                output = str(process.readAllStandardOutput(),
                             Preferences.getSystem("IOEncoding"),
                             'replace')
        
        if output:
            for line in output.splitlines():
                if line.startswith("commit "):
                    commitId = line.split()[1].strip()
                    return commitId
        
        return ""
    
    @pyqtSlot(QPoint)
    def on_logTree_customContextMenuRequested(self, pos):
        """
        Private slot to show the context menu of the log tree.
        
        @param pos position of the mouse pointer (QPoint)
        """
        self.__logTreeMenu.popup(self.logTree.mapToGlobal(pos))
    
    @pyqtSlot(QTreeWidgetItem, QTreeWidgetItem)
    def on_logTree_currentItemChanged(self, current, previous):
        """
        Private slot called, when the current item of the log tree changes.
        
        @param current reference to the new current item (QTreeWidgetItem)
        @param previous reference to the old current item (QTreeWidgetItem)
        """
        self.__updateToolMenuActions()
        
        # Highlight the current entry using a bold font
        for col in range(self.logTree.columnCount()):
            current and current.setFont(col, self.__logTreeBoldFont)
            previous and previous.setFont(col, self.__logTreeNormalFont)
        
        # set the state of the up and down buttons
        self.upButton.setEnabled(
            current is not None and
            self.logTree.indexOfTopLevelItem(current) > 0)
        self.downButton.setEnabled(
            current is not None and
            len(current.data(0, self.__parentsRole)) > 0 and
            (self.logTree.indexOfTopLevelItem(current) <
                self.logTree.topLevelItemCount() - 1 or
             self.nextButton.isEnabled()))
    
    @pyqtSlot()
    def on_logTree_itemSelectionChanged(self):
        """
        Private slot called, when the selection has changed.
        """
        self.__updateDetailsAndFiles()
        self.__updateSbsSelectLabel()
        self.__updateToolMenuActions()
        self.__generateDiffs()
    
    @pyqtSlot()
    def on_upButton_clicked(self):
        """
        Private slot to move the current item up one entry.
        """
        itm = self.logTree.itemAbove(self.logTree.currentItem())
        if itm:
            self.logTree.setCurrentItem(itm)
    
    @pyqtSlot()
    def on_downButton_clicked(self):
        """
        Private slot to move the current item down one entry.
        """
        itm = self.logTree.itemBelow(self.logTree.currentItem())
        if itm:
            self.logTree.setCurrentItem(itm)
        else:
            # load the next bunch and try again
            if self.nextButton.isEnabled():
                self.__addFinishCallback(self.on_downButton_clicked)
                self.on_nextButton_clicked()
    
    @pyqtSlot()
    def on_nextButton_clicked(self):
        """
        Private slot to handle the Next button.
        """
        if self.__skipEntries > 0 and self.nextButton.isEnabled():
            self.__getLogEntries(skip=self.__skipEntries)
    
    @pyqtSlot(QDate)
    def on_fromDate_dateChanged(self, date):
        """
        Private slot called, when the from date changes.
        
        @param date new date (QDate)
        """
        if self.__actionMode() == "filter":
            self.__filterLogs()
    
    @pyqtSlot(QDate)
    def on_toDate_dateChanged(self, date):
        """
        Private slot called, when the from date changes.
        
        @param date new date (QDate)
        """
        if self.__actionMode() == "filter":
            self.__filterLogs()
    
    @pyqtSlot(str)
    def on_fieldCombo_activated(self, txt):
        """
        Private slot called, when a new filter field is selected.
        
        @param txt text of the selected field (string)
        """
        if self.__actionMode() == "filter":
            self.__filterLogs()
    
    @pyqtSlot(str)
    def on_rxEdit_textChanged(self, txt):
        """
        Private slot called, when a filter expression is entered.
        
        @param txt filter expression (string)
        """
        if self.__actionMode() == "filter":
            self.__filterLogs()
        elif self.__actionMode() == "find":
            self.__findItem(self.__findBackwards, interactive=True)
    
    @pyqtSlot()
    def on_rxEdit_returnPressed(self):
        """
        Private slot handling a press of the Return key in the rxEdit input.
        """
        if self.__actionMode() == "find":
            self.__findItem(self.__findBackwards, interactive=True)
    
    @pyqtSlot(bool)
    def on_stopCheckBox_clicked(self, checked):
        """
        Private slot called, when the stop on copy/move checkbox is clicked.
        
        @param checked flag indicating the state of the check box (boolean)
        """
        self.vcs.getPlugin().setPreferences("StopLogOnCopy",
                                            self.stopCheckBox.isChecked())
        self.nextButton.setEnabled(True)
        self.limitSpinBox.setEnabled(True)
    
    ##################################################################
    ## Tool button menu action methods below
    ##################################################################
    
    @pyqtSlot()
    def __cherryActTriggered(self):
        """
        Private slot to handle the Copy Commits action.
        """
        commits = {}
        
        for itm in self.logTree.selectedItems():
            index = self.logTree.indexOfTopLevelItem(itm)
            commits[index] = itm.text(self.CommitIdColumn)
        
        if commits:
            pfile = e5App().getObject("Project").getProjectFile()
            lastModified = QFileInfo(pfile).lastModified().toString()
            shouldReopen = (
                self.vcs.gitCherryPick(
                    self.repodir,
                    [commits[i] for i in sorted(commits.keys(), reverse=True)]
                ) or
                QFileInfo(pfile).lastModified().toString() != lastModified
            )
            if shouldReopen:
                res = E5MessageBox.yesNo(
                    None,
                    self.tr("Copy Changesets"),
                    self.tr(
                        """The project should be reread. Do this now?"""),
                    yesDefault=True)
                if res:
                    e5App().getObject("Project").reopenProject()
                    return
            
            self.on_refreshButton_clicked()
    
    @pyqtSlot()
    def __tagActTriggered(self):
        """
        Private slot to tag the selected commit.
        """
        if len(self.logTree.selectedItems()) == 1:
            itm = self.logTree.selectedItems()[0]
            commit = itm.text(self.CommitIdColumn)
            tag = itm.text(self.TagsColumn).strip().split(", ", 1)[0]
            res = self.vcs.vcsTag(self.repodir, revision=commit, tagName=tag)
            if res:
                self.on_refreshButton_clicked()
    
    @pyqtSlot()
    def __switchActTriggered(self):
        """
        Private slot to switch the working directory to the
        selected commit.
        """
        if len(self.logTree.selectedItems()) == 1:
            itm = self.logTree.selectedItems()[0]
            commit = itm.text(self.CommitIdColumn)
            branches = [b for b in itm.text(self.BranchColumn).split(", ")
                        if "/" not in b]
            if len(branches) == 1:
                branch = branches[0]
            elif len(branches) > 1:
                branch, ok = QInputDialog.getItem(
                    self,
                    self.tr("Switch"),
                    self.tr("Select a branch"),
                    [""] + branches,
                    0, False)
                if not ok:
                    return
            else:
                branch = ""
            if branch:
                rev = branch
            else:
                rev = commit
            pfile = e5App().getObject("Project").getProjectFile()
            lastModified = QFileInfo(pfile).lastModified().toString()
            shouldReopen = (
                self.vcs.vcsUpdate(self.repodir, revision=rev) or
                QFileInfo(pfile).lastModified().toString() != lastModified
            )
            if shouldReopen:
                res = E5MessageBox.yesNo(
                    None,
                    self.tr("Switch"),
                    self.tr(
                        """The project should be reread. Do this now?"""),
                    yesDefault=True)
                if res:
                    e5App().getObject("Project").reopenProject()
                    return
            
            self.on_refreshButton_clicked()
    
    @pyqtSlot()
    def __branchActTriggered(self):
        """
        Private slot to create a new branch starting at the selected commit.
        """
        if len(self.logTree.selectedItems()) == 1:
            from .GitBranchDialog import GitBranchDialog
            itm = self.logTree.selectedItems()[0]
            commit = itm.text(self.CommitIdColumn)
            branches = [b for b in itm.text(self.BranchColumn).split(", ")
                        if "/" not in b]
            if len(branches) == 1:
                branch = branches[0]
            elif len(branches) > 1:
                branch, ok = QInputDialog.getItem(
                    self,
                    self.tr("Branch"),
                    self.tr("Select a default branch"),
                    [""] + branches,
                    0, False)
                if not ok:
                    return
            else:
                branch = ""
            res = self.vcs.gitBranch(
                self.repodir, revision=commit, branchName=branch,
                branchOp=GitBranchDialog.CreateBranch)
            if res:
                self.on_refreshButton_clicked()
    
    @pyqtSlot()
    def __branchSwitchActTriggered(self):
        """
        Private slot to create a new branch starting at the selected commit
        and switch the work tree to it.
        """
        if len(self.logTree.selectedItems()) == 1:
            from .GitBranchDialog import GitBranchDialog
            itm = self.logTree.selectedItems()[0]
            commit = itm.text(self.CommitIdColumn)
            branches = [b for b in itm.text(self.BranchColumn).split(", ")
                        if "/" not in b]
            if len(branches) == 1:
                branch = branches[0]
            elif len(branches) > 1:
                branch, ok = QInputDialog.getItem(
                    self,
                    self.tr("Branch & Switch"),
                    self.tr("Select a default branch"),
                    [""] + branches,
                    0, False)
                if not ok:
                    return
            else:
                branch = ""
            pfile = e5App().getObject("Project").getProjectFile()
            lastModified = QFileInfo(pfile).lastModified().toString()
            res, shouldReopen = self.vcs.gitBranch(
                self.repodir, revision=commit, branchName=branch,
                branchOp=GitBranchDialog.CreateSwitchBranch)
            shouldReopen = shouldReopen or \
                QFileInfo(pfile).lastModified().toString() != lastModified
            if res:
                if shouldReopen:
                    res = E5MessageBox.yesNo(
                        None,
                        self.tr("Switch"),
                        self.tr(
                            """The project should be reread. Do this now?"""),
                        yesDefault=True)
                    if res:
                        e5App().getObject("Project").reopenProject()
                        return
                
                self.on_refreshButton_clicked()
    
    @pyqtSlot()
    def __shortlogActTriggered(self):
        """
        Private slot to show a short log suitable for release announcements.
        """
        if len(self.logTree.selectedItems()) == 1:
            itm = self.logTree.selectedItems()[0]
            commit = itm.text(self.CommitIdColumn)
            branch = itm.text(self.BranchColumn).split(", ", 1)[0]
            branches = [b for b in itm.text(self.BranchColumn).split(", ")
                        if "/" not in b]
            if len(branches) == 1:
                branch = branches[0]
            elif len(branches) > 1:
                branch, ok = QInputDialog.getItem(
                    self,
                    self.tr("Show Short Log"),
                    self.tr("Select a branch"),
                    [""] + branches,
                    0, False)
                if not ok:
                    return
            else:
                branch = ""
            if branch:
                rev = branch
            else:
                rev = commit
            self.vcs.gitShortlog(self.repodir, commit=rev)
    
    @pyqtSlot()
    def __describeActTriggered(self):
        """
        Private slot to show the most recent tag reachable from a commit.
        """
        commits = []
        
        for itm in self.logTree.selectedItems():
            commits.append(itm.text(self.CommitIdColumn))
        
        if commits:
            self.vcs.gitDescribe(self.repodir, commits)
    
    ##################################################################
    ## Log context menu action methods below
    ##################################################################
    
    @pyqtSlot(bool)
    def __showCommitterColumns(self, on):
        """
        Private slot to show/hide the committer columns.
        
        @param on flag indicating the selection state (boolean)
        """
        self.logTree.setColumnHidden(self.CommitterColumn, not on)
        self.logTree.setColumnHidden(self.CommitDateColumn, not on)
        self.vcs.getPlugin().setPreferences("ShowCommitterColumns", on)
        self.__resizeColumnsLog()
    
    @pyqtSlot(bool)
    def __showAuthorColumns(self, on):
        """
        Private slot to show/hide the committer columns.
        
        @param on flag indicating the selection state (boolean)
        """
        self.logTree.setColumnHidden(self.AuthorColumn, not on)
        self.logTree.setColumnHidden(self.DateColumn, not on)
        self.vcs.getPlugin().setPreferences("ShowAuthorColumns", on)
        self.__resizeColumnsLog()
    
    @pyqtSlot(bool)
    def __showCommitIdColumn(self, on):
        """
        Private slot to show/hide the commit ID column.
        
        @param on flag indicating the selection state (boolean)
        """
        self.logTree.setColumnHidden(self.CommitIdColumn, not on)
        self.vcs.getPlugin().setPreferences("ShowCommitIdColumn", on)
        self.__resizeColumnsLog()
    
    @pyqtSlot(bool)
    def __showBranchesColumn(self, on):
        """
        Private slot to show/hide the branches column.
        
        @param on flag indicating the selection state (boolean)
        """
        self.logTree.setColumnHidden(self.BranchColumn, not on)
        self.vcs.getPlugin().setPreferences("ShowBranchesColumn", on)
        self.__resizeColumnsLog()
    
    @pyqtSlot(bool)
    def __showTagsColumn(self, on):
        """
        Private slot to show/hide the tags column.
        
        @param on flag indicating the selection state (boolean)
        """
        self.logTree.setColumnHidden(self.TagsColumn, not on)
        self.vcs.getPlugin().setPreferences("ShowTagsColumn", on)
        self.__resizeColumnsLog()
    
    ##################################################################
    ## Search and filter methods below
    ##################################################################
    
    def __actionMode(self):
        """
        Private method to get the selected action mode.
        
        @return selected action mode (string, one of filter or find)
        """
        return self.modeComboBox.itemData(
            self.modeComboBox.currentIndex())
    
    @pyqtSlot(int)
    def on_modeComboBox_currentIndexChanged(self, index):
        """
        Private slot to react on mode changes.
        
        @param index index of the selected entry (integer)
        """
        mode = self.modeComboBox.itemData(index)
        findMode = mode == "find"
        filterMode = mode == "filter"
        
        self.fromDate.setEnabled(filterMode)
        self.toDate.setEnabled(filterMode)
        self.findPrevButton.setVisible(findMode)
        self.findNextButton.setVisible(findMode)
        
        if findMode:
            for topIndex in range(self.logTree.topLevelItemCount()):
                self.logTree.topLevelItem(topIndex).setHidden(False)
            self.logTree.header().setSectionHidden(self.IconColumn, False)
        elif filterMode:
            self.__filterLogs()
    
    @pyqtSlot()
    def on_findPrevButton_clicked(self):
        """
        Private slot to find the previous item matching the entered criteria.
        """
        self.__findItem(True)
    
    @pyqtSlot()
    def on_findNextButton_clicked(self):
        """
        Private slot to find the next item matching the entered criteria.
        """
        self.__findItem(False)
    
    def __findItem(self, backwards=False, interactive=False):
        """
        Private slot to find an item matching the entered criteria.
        
        @param backwards flag indicating to search backwards (boolean)
        @param interactive flag indicating an interactive search (boolean)
        """
        self.__findBackwards = backwards
        
        fieldIndex, searchRx, indexIsRole = self.__prepareFieldSearch()
        currentIndex = self.logTree.indexOfTopLevelItem(
            self.logTree.currentItem())
        if backwards:
            if interactive:
                indexes = range(currentIndex, -1, -1)
            else:
                indexes = range(currentIndex - 1, -1, -1)
        else:
            if interactive:
                indexes = range(currentIndex, self.logTree.topLevelItemCount())
            else:
                indexes = range(currentIndex + 1,
                                self.logTree.topLevelItemCount())
        
        for index in indexes:
            topItem = self.logTree.topLevelItem(index)
            if indexIsRole:
                if fieldIndex == self.__changesRole:
                    changes = topItem.data(0, self.__changesRole)
                    txt = "\n".join(
                        [c["path"] for c in changes] +
                        [c["copyfrom"] for c in changes]
                    )
                else:
                    # Filter based on complete subject text
                    txt = topItem.data(0, self.__subjectRole)
            else:
                txt = topItem.text(fieldIndex)
            if searchRx.indexIn(txt) > -1:
                self.logTree.setCurrentItem(self.logTree.topLevelItem(index))
                break
        else:
            E5MessageBox.information(
                self,
                self.tr("Find Commit"),
                self.tr("""'{0}' was not found.""").format(self.rxEdit.text()))
    
    ##################################################################
    ## Commit navigation methods below
    ##################################################################
    
    def __commitIdClicked(self, url):
        """
        Private slot to handle the anchorClicked signal of the changeset
        details pane.
        
        @param url URL that was clicked
        @type QUrl
        """
        if url.scheme() == "rev":
            # a commit ID was clicked, show the respective item
            commitId = url.path()
            items = self.logTree.findItems(commitId, Qt.MatchStartsWith,
                                           self.CommitIdColumn)
            if items:
                itm = items[0]
                if itm.isHidden():
                    itm.setHidden(False)
                self.logTree.setCurrentItem(itm)
            else:
                # load the next batch and try again
                if self.nextButton.isEnabled():
                    self.__addFinishCallback(
                        lambda: self.__commitIdClicked(url))
                    self.on_nextButton_clicked()
    
    ###########################################################################
    ## Diff handling methods below
    ###########################################################################
    
    def __generateDiffs(self, parent=1):
        """
        Private slot to generate diff outputs for the selected item.
        
        @param parent number of parent to diff against
        @type int
        """
        self.diffEdit.clear()
        self.diffLabel.setText(self.tr("Differences"))
        self.diffSelectLabel.clear()
        try:
            self.diffHighlighter.regenerateRules()
        except AttributeError:
            # backward compatibility
            pass
        
        selectedItems = self.logTree.selectedItems()
        if len(selectedItems) == 1:
            currentItem = selectedItems[0]
            commit2 = currentItem.text(self.CommitIdColumn)
            parents = currentItem.data(0, self.__parentsRole)
            if len(parents) >= parent:
                self.diffLabel.setText(
                    self.tr("Differences to Parent {0}").format(parent))
                commit1 = parents[parent - 1]
                
                self.__diffGenerator.start(self.__filename, [commit1, commit2])
            
            if len(parents) > 1:
                parentLinks = []
                for index in range(1, len(parents) + 1):
                    if parent == index:
                        parentLinks.append("&nbsp;{0}&nbsp;".format(index))
                    else:
                        parentLinks.append(
                            '<a href="diff:{0}">&nbsp;{0}&nbsp;</a>'
                            .format(index))
                    self.diffSelectLabel.setText(
                        self.tr('Diff to Parent {0}')
                        .format(" ".join(parentLinks)))
        elif len(selectedItems) == 2:
            commit2 = selectedItems[0].text(self.CommitIdColumn)
            commit1 = selectedItems[1].text(self.CommitIdColumn)
            index2 = self.logTree.indexOfTopLevelItem(selectedItems[0])
            index1 = self.logTree.indexOfTopLevelItem(selectedItems[1])
            
            if index2 < index1:
                # swap to always compare old to new
                commit1, commit2 = commit2, commit1
            
            self.__diffGenerator.start(self.__filename, [commit1, commit2])
    
    def __generatorFinished(self):
        """
        Private slot connected to the finished signal of the diff generator.
        """
        diff, _, errors, fileSeparators = self.__diffGenerator.getResult()
        
        if diff:
            self.diffEdit.setPlainText("".join(diff))
        elif errors:
            self.diffEdit.setPlainText("".join(errors))
        else:
            self.diffEdit.setPlainText(self.tr('There is no difference.'))
        
        self.saveLabel.setVisible(bool(diff))
        
        fileSeparators = self.__mergeFileSeparators(fileSeparators)
        if self.__diffUpdatesFiles:
            for oldFileName, newFileName, lineNumber, _ in fileSeparators:
                if oldFileName == newFileName:
                    item = QTreeWidgetItem(self.filesTree, ["", oldFileName])
                elif oldFileName == "/dev/null":
                    item = QTreeWidgetItem(self.filesTree, ["", newFileName])
                else:
                    item = QTreeWidgetItem(
                        self.filesTree, ["", newFileName, "", "", oldFileName])
                item.setData(0, self.__diffFileLineRole, lineNumber)
            self.__resizeColumnsFiles()
            self.__resortFiles()
        else:
            for oldFileName, newFileName, lineNumber, _ in fileSeparators:
                for fileName in (oldFileName, newFileName):
                    if fileName != "/dev/null":
                        items = self.filesTree.findItems(
                            fileName, Qt.MatchExactly, 1)
                        for item in items:
                            item.setData(0, self.__diffFileLineRole,
                                         lineNumber)
        
        tc = self.diffEdit.textCursor()
        tc.movePosition(QTextCursor.Start)
        self.diffEdit.setTextCursor(tc)
        self.diffEdit.ensureCursorVisible()
    
    def __mergeFileSeparators(self, fileSeparators):
        """
        Private method to merge the file separator entries.
        
        @param fileSeparators list of file separator entries to be merged
        @return merged list of file separator entries
        """
        separators = {}
        for oldFile, newFile, pos1, pos2 in sorted(fileSeparators):
            if (oldFile, newFile) not in separators:
                separators[(oldFile, newFile)] = [oldFile, newFile, pos1, pos2]
            else:
                if pos1 != -2:
                    separators[(oldFile, newFile)][2] = pos1
                if pos2 != -2:
                    separators[(oldFile, newFile)][3] = pos2
        return list(separators.values())
    
    @pyqtSlot(QTreeWidgetItem, QTreeWidgetItem)
    def on_filesTree_currentItemChanged(self, current, previous):
        """
        Private slot called, when the current item of the files tree changes.
        
        @param current reference to the new current item (QTreeWidgetItem)
        @param previous reference to the old current item (QTreeWidgetItem)
        """
        if current:
            para = current.data(0, self.__diffFileLineRole)
            if para is not None:
                if para == 0:
                    tc = self.diffEdit.textCursor()
                    tc.movePosition(QTextCursor.Start)
                    self.diffEdit.setTextCursor(tc)
                    self.diffEdit.ensureCursorVisible()
                elif para == -1:
                    tc = self.diffEdit.textCursor()
                    tc.movePosition(QTextCursor.End)
                    self.diffEdit.setTextCursor(tc)
                    self.diffEdit.ensureCursorVisible()
                else:
                    # step 1: move cursor to end
                    tc = self.diffEdit.textCursor()
                    tc.movePosition(QTextCursor.End)
                    self.diffEdit.setTextCursor(tc)
                    self.diffEdit.ensureCursorVisible()
                    
                    # step 2: move cursor to desired line
                    tc = self.diffEdit.textCursor()
                    delta = tc.blockNumber() - para
                    tc.movePosition(QTextCursor.PreviousBlock,
                                    QTextCursor.MoveAnchor, delta)
                    self.diffEdit.setTextCursor(tc)
                    self.diffEdit.ensureCursorVisible()
    
    @pyqtSlot(str)
    def on_diffSelectLabel_linkActivated(self, link):
        """
        Private slot to handle the selection of a diff target.
        
        @param link activated link
        @type str
        """
        if ":" in link:
            scheme, parent = link.split(":", 1)
            if scheme == "diff":
                try:
                    parent = int(parent)
                    self.__generateDiffs(parent)
                except ValueError:
                    # ignore silently
                    pass
    
    @pyqtSlot(str)
    def on_saveLabel_linkActivated(self, link):
        """
        Private slot to handle the selection of the save link.
        
        @param link activated link
        @type str
        """
        if ":" not in link:
            return
        
        scheme, rest = link.split(":", 1)
        if scheme != "save" or rest != "me":
            return
        
        if self.projectMode:
            fname = self.vcs.splitPath(self.__filename)[0]
            fname += "/{0}.diff".format(os.path.split(fname)[-1])
        else:
            dname, fname = self.vcs.splitPath(self.__filename)
            if fname != '.':
                fname = "{0}.diff".format(self.__filename)
            else:
                fname = dname
        
        fname, selectedFilter = E5FileDialog.getSaveFileNameAndFilter(
            self,
            self.tr("Save Diff"),
            fname,
            self.tr("Patch Files (*.diff)"),
            None,
            E5FileDialog.Options(E5FileDialog.DontConfirmOverwrite))
        
        if not fname:
            return  # user aborted
        
        ext = QFileInfo(fname).suffix()
        if not ext:
            ex = selectedFilter.split("(*")[1].split(")")[0]
            if ex:
                fname += ex
        if QFileInfo(fname).exists():
            res = E5MessageBox.yesNo(
                self,
                self.tr("Save Diff"),
                self.tr("<p>The patch file <b>{0}</b> already exists."
                        " Overwrite it?</p>").format(fname),
                icon=E5MessageBox.Warning)
            if not res:
                return
        fname = Utilities.toNativeSeparators(fname)
        
        eol = e5App().getObject("Project").getEolString()
        try:
            f = open(fname, "w", encoding="utf-8", newline="")
            f.write(eol.join(self.diffEdit.toPlainText().splitlines()))
            f.write(eol)
            f.close()
        except IOError as why:
            E5MessageBox.critical(
                self, self.tr('Save Diff'),
                self.tr(
                    '<p>The patch file <b>{0}</b> could not be saved.'
                    '<br>Reason: {1}</p>')
                .format(fname, str(why)))
    
    @pyqtSlot(str)
    def on_sbsSelectLabel_linkActivated(self, link):
        """
        Private slot to handle selection of a side-by-side link.
        
        @param link text of the selected link
        @type str
        """
        if ":" in link:
            scheme, path = link.split(":", 1)
            if scheme == "sbsdiff" and "_" in path:
                commit1, commit2 = path.split("_", 1)
                self.vcs.gitSbsDiff(self.__filename,
                                    revisions=(commit1, commit2))