gitk: disable colours when calling git log
gitk: disable colours when calling git log

If the user specifies 'diff.color = 1' in their configuration file,
then gitk will not start.  Disable colours when calling git log.

Signed-off-by: Sam Vilain <9e3d9c151a1935fa51df4c7420358e0667b0b28d@catalyst.net.nz>
Signed-off-by: Shawn O. Pearce <f01032651c12a22b2103346ba96b3b6b231f9d3c@spearce.org>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git