DiffEditor: Save description along with diff.

Save complete, git-applicable patch when saving the result of
for example 'git show'. Strips some Creator-specific tags
off the description and reformats the description such
that it is accepted by git.

Change-Id: I739d85a7263f97e2149a2794974ba026f2eca067
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/diffeditor/diffeditorcontroller.h

@@ -57,6 +57,7 @@ public:
     bool isIgnoreWhitespace() const;
 
     QString makePatch(bool revert, bool addPrefix = false) const;
+    QString contents() const;
 
     DiffEditorReloader *reloader() const;
     void setReloader(DiffEditorReloader *reloader);