Git: Factor source directory resolving to a function

Change-Id: Ica2f6ad01052fb7130397740fcf2396de7cbbf9d
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>

src/plugins/git/giteditor.h

@@ -77,6 +77,7 @@ private:
     QString revisionSubject(const QTextBlock &inBlock) const;
     bool supportChangeLinks() const;
     QString fileNameForLine(int line) const;
+    QString sourceWorkingDirectory() const;
 
     mutable QRegExp m_changeNumberPattern;
     QString m_currentChange;