VCS[perforce,svn,vcs]: Use convenience to tag editors for reuse.

Introduce convenience to determine editor tags to avoid
crashes on empty files arguments, etc (VCSBaseEditor).
Add diff-whitespace handling and 'Revert chunk' to Perforce.

Task-number: QTCREATORBUG-4305

6 files changed, 165 insertions, 79 deletions

diff --git a/src/plugins/cvs/cvsplugin.cpp b/src/plugins/cvs/cvsplugin.cpp
index 26b4c520267..30dd956d2b4 100644
--- a/src/plugins/cvs/cvsplugin.cpp
+++ b/src/plugins/cvs/cvsplugin.cpp
@@ -155,14 +155,6 @@ static inline QString debugCodec(const QTextCodec *c)
     return c ? QString::fromAscii(c->name()) : QString::fromAscii("Null codec");
 }
 
-Core::IEditor* locateEditor(const char *property, const QString &entry)
-{
-    foreach (Core::IEditor *ed, Core::EditorManager::instance()->openedEditors())
-        if (ed->property(property).toString() == entry)
-            return ed;
-    return 0;
-}
-
 static inline bool messageBoxQuestion(const QString &title, const QString &question, QWidget *parent = 0)
 {
     return QMessageBox::question(parent, title, question, QMessageBox::Yes|QMessageBox::No) == QMessageBox::Yes;
@@ -535,12 +527,9 @@ static inline void setDiffBaseDirectory(Core::IEditor *editor, const QString &db
 // with a diff editor and re-run the diff with parameters.
 struct CvsDiffParameters
 {
-    CvsDiffParameters() : reUseEditor(false) {}
-
     QString workingDir;
     QStringList arguments;
     QStringList files;
-    bool reUseEditor;
 };
 
 // Parameter widget controlling whitespace diff mode, associated with a parameter
@@ -574,7 +563,6 @@ CvsDiffParameterWidget::CvsDiffParameterWidget(const CvsDiffParameters &p, QWidg
 void CvsDiffParameterWidget::triggerReRun()
 {
     CvsDiffParameters effectiveParameters = m_parameters;
-    effectiveParameters.reUseEditor = true;
     effectiveParameters.arguments = arguments();
     emit reRunDiff(effectiveParameters);
 }
@@ -617,18 +605,17 @@ void CVSPlugin::cvsDiff(const CvsDiffParameters &p)
         output = tr("The files do not differ.");
     // diff of a single file? re-use an existing view if possible to support
     // the common usage pattern of continuously changing and diffing a file
-    if (p.files.count() == 1 || p.reUseEditor) {
-        // Show in the same editor if diff has been executed before
-        if (Core::IEditor *editor = locateEditor("originalFileName", id)) {
-            editor->createNew(output);
-            Core::EditorManager::instance()->activateEditor(editor, Core::EditorManager::ModeSwitch);
-            setDiffBaseDirectory(editor, p.workingDir);
-            return;
-        }
+    // Show in the same editor if diff has been executed before
+    const QString tag = VCSBase::VCSBaseEditorWidget::editorTag(VCSBase::DiffOutput, p.workingDir, p.files);
+    if (Core::IEditor *existingEditor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(tag)) {
+        existingEditor->createNew(output);
+        Core::EditorManager::instance()->activateEditor(existingEditor, Core::EditorManager::ModeSwitch);
+        setDiffBaseDirectory(existingEditor, p.workingDir);
+        return;
     }
     const QString title = QString::fromLatin1("cvs diff %1").arg(id);
     Core::IEditor *editor = showOutputInEditor(title, output, VCSBase::DiffOutput, source, codec);
-    editor->setProperty("originalFileName", id);
+    VCSBase::VCSBaseEditorWidget::tagEditor(editor, tag);
     setDiffBaseDirectory(editor, p.workingDir);
     CVSEditor *diffEditorWidget = qobject_cast<CVSEditor*>(editor->widget());
     QTC_ASSERT(diffEditorWidget, return ; )
@@ -893,13 +880,14 @@ void CVSPlugin::filelog(const QString &workingDir,
 
     // Re-use an existing view if possible to support
     // the common usage pattern of continuously changing and diffing a file
-    if (Core::IEditor *editor = locateEditor("logFileName", id)) {
+    const QString tag = VCSBase::VCSBaseEditorWidget::editorTag(VCSBase::LogOutput, workingDir, files);
+    if (Core::IEditor *editor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(tag)) {
         editor->createNew(response.stdOut);
         Core::EditorManager::instance()->activateEditor(editor, Core::EditorManager::ModeSwitch);
     } else {
         const QString title = QString::fromLatin1("cvs log %1").arg(id);
         Core::IEditor *newEditor = showOutputInEditor(title, response.stdOut, VCSBase::LogOutput, source, codec);
-        newEditor->setProperty("logFileName", id);
+        VCSBase::VCSBaseEditorWidget::tagEditor(newEditor, tag);
         if (enableAnnotationContextMenu)
             VCSBase::VCSBaseEditorWidget::getVcsBaseEditor(newEditor)->setFileLogAnnotateEnabled(true);
     }
@@ -1034,14 +1022,15 @@ void CVSPlugin::annotate(const QString &workingDir, const QString &file,
     if (lineNumber < 1)
         lineNumber = VCSBase::VCSBaseEditorWidget::lineNumberOfCurrentEditor(file);
 
-    if (Core::IEditor *editor = locateEditor("annotateFileName", id)) {
+    const QString tag = VCSBase::VCSBaseEditorWidget::editorTag(VCSBase::AnnotateOutput, workingDir, QStringList(file), revision);
+    if (Core::IEditor *editor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(tag)) {
         editor->createNew(response.stdOut);
         VCSBase::VCSBaseEditorWidget::gotoLineOfEditor(editor, lineNumber);
         Core::EditorManager::instance()->activateEditor(editor, Core::EditorManager::ModeSwitch);
     } else {
         const QString title = QString::fromLatin1("cvs annotate %1").arg(id);
         Core::IEditor *newEditor = showOutputInEditor(title, response.stdOut, VCSBase::AnnotateOutput, source, codec);
-        newEditor->setProperty("annotateFileName", id);
+        VCSBase::VCSBaseEditorWidget::tagEditor(newEditor, tag);
         VCSBase::VCSBaseEditorWidget::gotoLineOfEditor(newEditor, lineNumber);
     }
 }
@@ -1230,14 +1219,14 @@ bool CVSPlugin::describe(const QString &repositoryPath,
     // Re-use an existing view if possible to support
     // the common usage pattern of continuously changing and diffing a file
     const QString commitId = entries.front().revisions.front().commitId;
-    if (Core::IEditor *editor = locateEditor("describeChange", commitId)) {
+    if (Core::IEditor *editor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(commitId)) {
         editor->createNew(output);
         Core::EditorManager::instance()->activateEditor(editor, Core::EditorManager::ModeSwitch);
         setDiffBaseDirectory(editor, repositoryPath);
     } else {
         const QString title = QString::fromLatin1("cvs describe %1").arg(commitId);
         Core::IEditor *newEditor = showOutputInEditor(title, output, VCSBase::DiffOutput, entries.front().file, codec);
-        newEditor->setProperty("describeChange", commitId);
+        VCSBase::VCSBaseEditorWidget::tagEditor(newEditor, commitId);
         setDiffBaseDirectory(newEditor, repositoryPath);
     }
     return true;
diff --git a/src/plugins/perforce/perforceplugin.cpp b/src/plugins/perforce/perforceplugin.cpp
index 24e83723f99..0f412356873 100644
--- a/src/plugins/perforce/perforceplugin.cpp
+++ b/src/plugins/perforce/perforceplugin.cpp
@@ -60,6 +60,7 @@
 #include <vcsbase/basevcssubmiteditorfactory.h>
 #include <vcsbase/vcsbaseeditor.h>
 #include <vcsbase/vcsbaseoutputwindow.h>
+#include <vcsbase/vcsbaseeditorparameterwidget.h>
 
 #include <QtCore/QtPlugin>
 #include <QtCore/QDebug>
@@ -1213,32 +1214,74 @@ void PerforcePlugin::slotSubmitDiff(const QStringList &files)
     p4Diff(m_commitWorkingDirectory, files);
 }
 
-void PerforcePlugin::p4Diff(const QString &workingDir, const QStringList &files)
+struct PerforceDiffParameters
 {
-    Core::IEditor *existingEditor = 0;
+    QString workingDir;
+    QStringList diffArguments;
+    QStringList files;
+};
 
-    QTextCodec *codec = VCSBase::VCSBaseEditorWidget::getCodec(workingDir, files);
-    const QString id = VCSBase::VCSBaseEditorWidget::getTitleId(workingDir, files);
-    const QString source = VCSBase::VCSBaseEditorWidget::getSource(workingDir, files);
+// Parameter widget controlling whitespace diff mode, associated with a parameter
+class PerforceDiffParameterWidget : public VCSBase::VCSBaseEditorParameterWidget
+{
+    Q_OBJECT
+public:
+    explicit PerforceDiffParameterWidget(const PerforceDiffParameters &p, QWidget *parent = 0);
+
+signals:
+    void reRunDiff(const Perforce::Internal::PerforceDiffParameters &);
+
+private slots:
+    void triggerReRun();
+
+private:
+    const PerforceDiffParameters m_parameters;
+};
+
+PerforceDiffParameterWidget::PerforceDiffParameterWidget(const PerforceDiffParameters &p, QWidget *parent) :
+    VCSBase::VCSBaseEditorParameterWidget(parent), m_parameters(p)
+{
+    setBaseArguments(p.diffArguments);
+    addIgnoreWhiteSpaceButton(QString(QLatin1Char('w')));
+    connect(this, SIGNAL(argumentsChanged()), this, SLOT(triggerReRun()));
+}
+
+void PerforceDiffParameterWidget::triggerReRun()
+{
+    PerforceDiffParameters effectiveParameters = m_parameters;
+    effectiveParameters.diffArguments = arguments();
+    emit reRunDiff(effectiveParameters);
+}
 
+void PerforcePlugin::p4Diff(const QString &workingDir, const QStringList &files)
+{
+    PerforceDiffParameters p;
+    p.workingDir = workingDir;
+    p.files = files;
+    p.diffArguments.push_back(QString(QLatin1Char('u')));
+    p4Diff(p);
+}
+
+void PerforcePlugin::p4Diff(const PerforceDiffParameters &p)
+{
+    QTextCodec *codec = VCSBase::VCSBaseEditorWidget::getCodec(p.workingDir, p.files);
+    const QString id = VCSBase::VCSBaseEditorWidget::getTitleId(p.workingDir, p.files);
     // Reuse existing editors for that id
-    foreach (Core::IEditor *ed, Core::EditorManager::instance()->openedEditors()) {
-        if (ed->file()->property("originalFileName").toString() == id) {
-            existingEditor = ed;
-            break;
-        }
-    }
+    const QString tag = VCSBase::VCSBaseEditorWidget::editorTag(VCSBase::DiffOutput, p.workingDir, p.files);
+    Core::IEditor *existingEditor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(tag);
     // Split arguments according to size
     QStringList args;
-    args << QLatin1String("diff") << QLatin1String("-du");
+    args << QLatin1String("diff");
+    if (!p.diffArguments.isEmpty()) // -duw..
+        args << (QLatin1String("-d") + p.diffArguments.join(QString()));
     QStringList extraArgs;
-    if (files.size() > 1) {
-        extraArgs = files;
+    if (p.files.size() > 1) {
+        extraArgs = p.files;
     } else {
-        args.append(files);
+        args.append(p.files);
     }
     const unsigned flags = CommandToWindow|StdErrToWindow|ErrorToWindow|OverrideDiffEnvironment;
-    const PerforceResponse result = runP4Cmd(workingDir, args, flags,
+    const PerforceResponse result = runP4Cmd(p.workingDir, args, flags,
                                              extraArgs, QByteArray(), codec);
     if (result.error)
         return;
@@ -1246,12 +1289,23 @@ void PerforcePlugin::p4Diff(const QString &workingDir, const QStringList &files)
     if (existingEditor) {
         existingEditor->createNew(result.stdOut);
         Core::EditorManager::instance()->activateEditor(existingEditor, Core::EditorManager::ModeSwitch);
-    } else {
-        Core::IEditor *editor = showOutputInEditor(tr("p4 diff %1").arg(id), result.stdOut, VCSBase::DiffOutput,
-                                                   VCSBase::VCSBaseEditorWidget::getSource(workingDir, files),
-                                                   codec);
-        editor->file()->setProperty("originalFileName", id);
+        return;
     }
+    // Create new editor
+    Core::IEditor *editor = showOutputInEditor(tr("p4 diff %1").arg(id), result.stdOut, VCSBase::DiffOutput,
+                                               VCSBase::VCSBaseEditorWidget::getSource(p.workingDir, p.files),
+                                               codec);
+    VCSBase::VCSBaseEditorWidget::tagEditor(editor, tag);
+    VCSBase::VCSBaseEditorWidget *diffEditorWidget = qobject_cast<VCSBase::VCSBaseEditorWidget *>(editor->widget());
+    // Wire up the parameter widget to trigger a re-run on
+    // parameter change and 'revert' from inside the diff editor.
+    diffEditorWidget->setRevertDiffChunkEnabled(true);
+    PerforceDiffParameterWidget *pw = new PerforceDiffParameterWidget(p);
+    connect(pw, SIGNAL(reRunDiff(Perforce::Internal::PerforceDiffParameters)),
+            this, SLOT(p4Diff(Perforce::Internal::PerforceDiffParameters)));
+    connect(diffEditorWidget, SIGNAL(diffChunkReverted(VCSBase::DiffChunk)),
+            pw, SLOT(triggerReRun()));
+    diffEditorWidget->setConfigurationWidget(pw);
 }
 
 void PerforcePlugin::describe(const QString & source, const QString &n)
@@ -1498,3 +1552,5 @@ void PerforcePlugin::getTopLevel()
 }
 
 Q_EXPORT_PLUGIN(Perforce::Internal::PerforcePlugin)
+
+#include "perforceplugin.moc"
diff --git a/src/plugins/perforce/perforceplugin.h b/src/plugins/perforce/perforceplugin.h
index e7558c04b23..23186bd3884 100644
--- a/src/plugins/perforce/perforceplugin.h
+++ b/src/plugins/perforce/perforceplugin.h
@@ -63,7 +63,7 @@ namespace Locator {
 
 namespace Perforce {
 namespace Internal {
-
+struct PerforceDiffParameters;
 class PerforceVersionControl;
 
 struct PerforceResponse
@@ -111,6 +111,7 @@ public:
 public slots:
     void describe(const QString &source, const QString &n);
     void vcsAnnotate(const QString &file, const QString &revision /* = QString() */, int lineNumber);
+    void p4Diff(const Perforce::Internal::PerforceDiffParameters &p);
 
 private slots:
     void openCurrentFile();
diff --git a/src/plugins/subversion/subversionplugin.cpp b/src/plugins/subversion/subversionplugin.cpp
index 4b2b1503d78..97e3a9099db 100644
--- a/src/plugins/subversion/subversionplugin.cpp
+++ b/src/plugins/subversion/subversionplugin.cpp
@@ -153,14 +153,6 @@ static inline QString debugCodec(const QTextCodec *c)
     return c ? QString::fromAscii(c->name()) : QString::fromAscii("Null codec");
 }
 
-Core::IEditor* locateEditor(const char *property, const QString &entry)
-{
-    foreach (Core::IEditor *ed, Core::EditorManager::instance()->openedEditors())
-        if (ed->property(property).toString() == entry)
-            return ed;
-    return 0;
-}
-
 // Parse "svn status" output for added/modified/deleted files
 // "M<7blanks>file"
 typedef QList<SubversionSubmitEditor::StatusFilePair> StatusList;
@@ -540,13 +532,10 @@ void SubversionPlugin::diffCommitFiles(const QStringList &files)
 // with a diff editor and re-run the diff with parameters.
 struct SubversionDiffParameters
 {
-    SubversionDiffParameters() : reUseEditor(false) {}
-
     QString workingDir;
     QStringList arguments;
     QStringList files;
     QString diffName;
-    bool reUseEditor;
 };
 
 // Parameter widget controlling whitespace diff mode, associated with a parameter
@@ -577,7 +566,6 @@ SubversionDiffParameterWidget::SubversionDiffParameterWidget(const SubversionDif
 void SubversionDiffParameterWidget::triggerReRun()
 {
     SubversionDiffParameters effectiveParameters = m_parameters;
-    effectiveParameters.reUseEditor = true;
     // Subversion wants" -x -<ext-args>", default being -u
     const QStringList a = arguments();
     if (!a.isEmpty())
@@ -621,20 +609,18 @@ void SubversionPlugin::svnDiff(const Subversion::Internal::SubversionDiffParamet
 
     // diff of a single file? re-use an existing view if possible to support
     // the common usage pattern of continuously changing and diffing a file
-    if (p.files.count() == 1 || p.reUseEditor) {
-        // Show in the same editor if diff has been executed before
-        if (Core::IEditor *editor = locateEditor("originalFileName", p.files.front())) {
-            editor->createNew(response.stdOut);
-            Core::EditorManager::instance()->activateEditor(editor, Core::EditorManager::ModeSwitch);
-            setDiffBaseDirectory(editor, p.workingDir);
-            return;
-        }
+    const QString tag = VCSBase::VCSBaseEditorWidget::editorTag(VCSBase::DiffOutput, p.workingDir, p.files);
+    // Show in the same editor if diff has been executed before
+    if (Core::IEditor *existingEditor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(tag)) {
+        existingEditor->createNew(response.stdOut);
+        Core::EditorManager::instance()->activateEditor(existingEditor, Core::EditorManager::ModeSwitch);
+        setDiffBaseDirectory(existingEditor, p.workingDir);
+        return;
     }
     const QString title = QString::fromLatin1("svn diff %1").arg(diffName);
     Core::IEditor *editor = showOutputInEditor(title, response.stdOut, VCSBase::DiffOutput, source, codec);
     setDiffBaseDirectory(editor, p.workingDir);
-    if (p.files.count() == 1)
-        editor->setProperty("originalFileName", p.files.front());
+    VCSBase::VCSBaseEditorWidget::tagEditor(editor, tag);
     SubversionEditor *diffEditorWidget = qobject_cast<SubversionEditor *>(editor->widget());
     QTC_ASSERT(diffEditorWidget, return ; )
 
@@ -938,14 +924,15 @@ void SubversionPlugin::filelog(const QString &workingDir,
     // the common usage pattern of continuously changing and diffing a file
 
     const QString id = VCSBase::VCSBaseEditorWidget::getTitleId(workingDir, files);
-    if (Core::IEditor *editor = locateEditor("logFileName", id)) {
+    const QString tag = VCSBase::VCSBaseEditorWidget::editorTag(VCSBase::LogOutput, workingDir, files);
+    if (Core::IEditor *editor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(tag)) {
         editor->createNew(response.stdOut);
         Core::EditorManager::instance()->activateEditor(editor, Core::EditorManager::ModeSwitch);
     } else {
         const QString title = QString::fromLatin1("svn log %1").arg(id);
         const QString source = VCSBase::VCSBaseEditorWidget::getSource(workingDir, files);
         Core::IEditor *newEditor = showOutputInEditor(title, response.stdOut, VCSBase::LogOutput, source, /*codec*/0);
-        newEditor->setProperty("logFileName", id);
+        VCSBase::VCSBaseEditorWidget::tagEditor(newEditor, tag);
         if (enableAnnotationContextMenu)
             VCSBase::VCSBaseEditorWidget::getVcsBaseEditor(newEditor)->setFileLogAnnotateEnabled(true);
     }
@@ -1012,16 +999,17 @@ void SubversionPlugin::vcsAnnotate(const QString &workingDir, const QString &fil
     if (lineNumber <= 0)
         lineNumber = VCSBase::VCSBaseEditorWidget::lineNumberOfCurrentEditor(source);
     // Determine id
-    const QString id = VCSBase::VCSBaseEditorWidget::getTitleId(workingDir, QStringList(file), revision);
-
-    if (Core::IEditor *editor = locateEditor("annotateFileName", id)) {
+    const QStringList files = QStringList(file);
+    const QString id = VCSBase::VCSBaseEditorWidget::getTitleId(workingDir, files, revision);
+    const QString tag = VCSBase::VCSBaseEditorWidget::editorTag(VCSBase::AnnotateOutput, workingDir, files);
+    if (Core::IEditor *editor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(tag)) {
         editor->createNew(response.stdOut);
         VCSBase::VCSBaseEditorWidget::gotoLineOfEditor(editor, lineNumber);
         Core::EditorManager::instance()->activateEditor(editor, Core::EditorManager::ModeSwitch);
     } else {
         const QString title = QString::fromLatin1("svn annotate %1").arg(id);
         Core::IEditor *newEditor = showOutputInEditor(title, response.stdOut, VCSBase::AnnotateOutput, source, codec);
-        newEditor->setProperty("annotateFileName", id);
+        VCSBase::VCSBaseEditorWidget::tagEditor(newEditor, tag);
         VCSBase::VCSBaseEditorWidget::gotoLineOfEditor(newEditor, lineNumber);
     }
 }
@@ -1079,13 +1067,14 @@ void SubversionPlugin::describe(const QString &source, const QString &changeNr)
     // Re-use an existing view if possible to support
     // the common usage pattern of continuously changing and diffing a file
     const QString id = diffArg + source;
-    if (Core::IEditor *editor = locateEditor("describeChange", id)) {
+    const QString tag = VCSBase::VCSBaseEditorWidget::editorTag(VCSBase::DiffOutput, source, QStringList(), changeNr);
+    if (Core::IEditor *editor = VCSBase::VCSBaseEditorWidget::locateEditorByTag(tag)) {
         editor->createNew(description);
         Core::EditorManager::instance()->activateEditor(editor, Core::EditorManager::ModeSwitch);
     } else {
         const QString title = QString::fromLatin1("svn describe %1#%2").arg(fi.fileName(), changeNr);
         Core::IEditor *newEditor = showOutputInEditor(title, description, VCSBase::DiffOutput, source, codec);
-        newEditor->setProperty("describeChange", id);
+        VCSBase::VCSBaseEditorWidget::tagEditor(newEditor, tag);
     }
 }
 
diff --git a/src/plugins/vcsbase/vcsbaseeditor.cpp b/src/plugins/vcsbase/vcsbaseeditor.cpp
index b8a97fa72ec..add1da01cfb 100644
--- a/src/plugins/vcsbase/vcsbaseeditor.cpp
+++ b/src/plugins/vcsbase/vcsbaseeditor.cpp
@@ -1068,6 +1068,49 @@ void VCSBaseEditorWidget::slotRevertDiffChunk()
         emit diffChunkReverted(chunk);
 }
 
+// Tagging of editors for re-use.
+QString VCSBaseEditorWidget::editorTag(EditorContentType t,
+                                       const QString &workingDirectory,
+                                       const QStringList &files,
+                                       const QString &revision)
+{
+    const QChar colon = QLatin1Char(':');
+    QString rc = QString::number(t);
+    rc += colon;
+    if (!revision.isEmpty()) {
+        rc += revision;
+        rc += colon;
+    }
+    rc += workingDirectory;
+    if (!files.isEmpty()) {
+        rc += colon;
+        rc += files.join(QString(colon));
+    }
+    return rc;
+}
+
+static const char tagPropertyC[] = "_q_VCSBaseEditorTag";
+
+void VCSBaseEditorWidget::tagEditor(Core::IEditor *e, const QString &tag)
+{
+    e->setProperty(tagPropertyC, QVariant(tag));
+}
+
+Core::IEditor* VCSBaseEditorWidget::locateEditorByTag(const QString &tag)
+{
+    Core::IEditor *rc = 0;
+    foreach (Core::IEditor *ed, Core::EditorManager::instance()->openedEditors()) {
+        const QVariant tagPropertyValue = ed->property(tagPropertyC);
+        if (tagPropertyValue.type() == QVariant::String && tagPropertyValue.toString() == tag) {
+            rc = ed;
+            break;
+        }
+    }
+    if (VCSBase::Constants::Internal::debug)
+        qDebug() << "locateEditorByTag " << tag << rc;
+    return rc;
+}
+
 } // namespace VCSBase
 
 #include "vcsbaseeditor.moc"
diff --git a/src/plugins/vcsbase/vcsbaseeditor.h b/src/plugins/vcsbase/vcsbaseeditor.h
index 607512b7d0d..d5df5338b34 100644
--- a/src/plugins/vcsbase/vcsbaseeditor.h
+++ b/src/plugins/vcsbase/vcsbaseeditor.h
@@ -186,6 +186,14 @@ public:
     bool setConfigurationWidget(QWidget *w);
     QWidget *configurationWidget() const;
 
+    /* Tagging editors: Sometimes, an editor should be re-used, for example, when showing
+     * a diff of the same file with different diff-options. In order to be able to find
+     * the editor, they get a 'tag' containing type and parameters (dynamic property string). */
+    static void tagEditor(Core::IEditor *e, const QString &tag);
+    static Core::IEditor* locateEditorByTag(const QString &tag);
+    static QString editorTag(EditorContentType t, const QString &workingDirectory, const QStringList &files,
+                             const QString &revision = QString());
+
 signals:
     // These signals also exist in the opaque editable (IEditor) that is
     // handled by the editor manager for convenience. They are emitted