DiffEditor: fix revert chunk for diffs of modified files

Apply chunk action doesn't make sense for that case,
will stay disabled.

Task-number: QTCREATORBUG-17136
Change-Id: Idce31b3aa9d354536a01607c10b20273158961d5
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/diffeditor/diffutils.h

@@ -38,12 +38,18 @@ class Diff;
 
 class DIFFEDITOR_EXPORT DiffFileInfo {
 public:
+    enum PatchBehaviour {
+        PatchFile,
+        PatchEditor
+    };
+
     DiffFileInfo() {}
     DiffFileInfo(const QString &file) : fileName(file) {}
     DiffFileInfo(const QString &file, const QString &type)
         : fileName(file), typeInfo(type) {}
     QString fileName;
     QString typeInfo;
+    PatchBehaviour patchBehaviour = PatchFile;
 };
 
 class DIFFEDITOR_EXPORT TextLineData {