cros-workon: properly fetch branches as well

Currently, we don't specify branches in cros-workon at all. This causes
issues in minilayout, as git-2 eclass will by default only download
commits from master, unless specified in EGIT_BRANCH.
There's no way to fix this directly since we don't know the branch we're
on, so we'll just force download of all via a tricky branch spec.

BUG=chromium-os:35136
TEST=emerge kernel
TEST=manually verify that "git fetch :" acts correctly, eg. downloads all
commits, unlike "git fetch master:master".

Change-Id: I211affed15f054b20c688502105ee9b3a0849270
Reviewed-on: https://gerrit.chromium.org/gerrit/35640
Commit-Ready: Zdenek Behan <zbehan@chromium.org>
Reviewed-by: Zdenek Behan <zbehan@chromium.org>
Tested-by: Zdenek Behan <zbehan@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/35720
Tested-by: David James <davidjames@chromium.org>
1 file changed