git now takes an optional parameter for -t

Bug: 1288010
Change-Id: I0b7b212229f8df846a2d80a1632387982fd7358e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3395441
Auto-Submit: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Commit-Queue: Dirk Pranke <dpranke@google.com>