git-sync-deps: Switch shallow/deep to be command-line arg, flip default

Nearly everyone that runs this just needs the shallow behavior. Having
it tied to a command-line arg seems simpler, too.

Change-Id: Ife73580e1fb90394ef6971222724d6b72f42760e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/804398
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed