list_commands(): simplify code by using chdir()
list_commands(): simplify code by using chdir()

The current code builds absolute path strings for each file to
stat(), this can easily be avoided by chdir()ing into the directory.

Signed-off-by: Scott R Parish <a33d8d465abb7cc30958b4709552861983c28f02@srparish.net>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

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