Adjust SHA1 output.
Adjust SHA1 output.

Specifically, add it into GerritPatch, and limit the sha1 output
to just the first 8 chars (git norm)- good enough for normal usage.

BUG=None
TEST=./run_tests.sh

Change-Id: Id3556a5ba6b3a840a3f39efa6cdf98bcf6065d23
Reviewed-on: https://gerrit.chromium.org/gerrit/20815
Tested-by: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Commit-Ready: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>

zhang0137/chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,coreos/chromite,coreos/chromite,zhang0137/chromite,coreos/chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite