bug#2982: 23.0.92; `vc-diff' behaves inconsistently with git

[Markus Triska]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>  In the case of git, it would be easier to ask git the status

Exactly, after what you explained before, it seems to me that Emacs
should ask git for the status of the file right after saving as well,
and store the new modification time (you explained that it already does
it after opening). Of course, this does not solve the problem of
external modtime changes, but it seems that this is solvable as well:
Before running diff, Emacs could ask git whether the status has changed.
It seems that this would yield consistent behaviour of vc-diff
regardless of whether the file was just opened or saved in between.