Restore --head/-H to gclient
Restore --head/-H to gclient

R=dmazzoni@chromium.org, maruel@chromium.org
BUG=109184

Review-Url: https://codereview.chromium.org/2105493002

CoherentLabs/depot_tools,primiano/depot_tools,CoherentLabs/depot_tools,primiano/depot_tools,primiano/depot_tools