Add repo sync support for GITC checkouts. If the user is in the
GITC client directory they can still pull the sources as normal
if they pass in the --force-gitc argument. Otherwise the user
should call repo sync in the GITC view to update the user's
remote view. (This works because .repo in the GITC view will
link to .repo in the client config directory.)
Part of the support for this change is the refactoring of GITC
related code into gitc_utils.py.
Change-Id: I2636aaa50b450b6f091309db8dd0e8f4dbdad579
