c21398be6d
When comparing a string of commits, when we find two non-merge commits
that differ, we now write the two commits to files and diff the files.
This pulls out the logic for creating a temporary directory from
external_diff into a separate procedure so that the new diffcommits
procedure can use it.
Because the diff command returns an exit status of 1 when the files
differ, and Tcl treats that as an error, this adds catch {} around the
close statements in getblobdiffline.
At present this only removes the temporary files when gitk exits. It
should remove them when the diff is done.
Signed-off-by: Paul Mackerras <paulus@samba.org>