Improve label of index version in compare editors
When opening the compare editor from the staging view for an unstaged
file, the right side shows the Index version.
The problem is that not many people discover that it is in fact editable
(and the way to do partial staging).
This change tries to help a bit by changing the label from
file.txt Index ()
to
Index: file.txt (editable)
Index is used as a prefix because the left side is "Local: file.txt".
"(editable)" is not appended in case of non-editable (stage != 0), see
bug 391856.
Bug: 398562
Change-Id: I9940d2f148393b1f4704664e379c5c863565a118
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>