Fixes: Make git diff work for staged files, do not launch submit if file list empty, make file model read only, add conveniences

Details: Add a type data field to the git file model

src/plugins/git/commitdata.h

@@ -77,6 +77,8 @@ struct CommitData
     // from a git status output
     bool parseFilesFromStatus(const QString &output);
 
+    bool filesEmpty() const;
+
     // Convenience to retrieve the file names from
     // the specification list. Optionally filter for a certain state
     QStringList stagedFileNames(const QString &stateFilter = QString()) const;