rhg: Colored output is not supported
Fallback if it is requested explicitly.
The default is documented as use color "whenever it seems possible".
rhg proceeds without color in that case.
Differential Revision: https://phab.mercurial-scm.org/D11762
#require execbit
$ hg init repo
$ cd repo
$ echo foo > foo
$ chmod 644 foo
$ hg ci -qAm '644'
$ chmod 755 foo
$ hg ci -qAm '755'
reverting to rev 0
$ hg revert -a -r 0
reverting foo
$ hg st
M foo
$ hg diff --git
diff --git a/foo b/foo
old mode 100755
new mode 100644
$ cd ..