Create v8 roll branches in refs/heads.

Create v8 roll branches in refs/heads.

This is needed as normal chromium checkouts don't fetch
branch-heads.

These branches will also be replicated by GitHub and are
fetched when cloning from the repository.

The expected object size will be the same or smaller than
before as we currently push the same information onto the
candidates branch (which already is in refs/heads). The only
difference is the increasing number of refs in refs/heads.

BUG=chromium:451975
TBR=tandrii@chromium.org
NOTRY=true
LOG=n

TEST=./script_test.py
TEST=tools/release/create_release.py -r machenbach@chromium.org -a machenbach@chromium.org --dry-run

Committed: https://crrev.com/44bc8646c3316ef75f00be9c404eccf6ca586505
Cr-Commit-Position: refs/heads/master@{#26629}

[Michael Achenbach, 2015-02-11 11:12:46]

machenbach@chromium.org changed reviewers:
+ tandrii@chromium.org

[Michael Achenbach, 2015-02-11 11:24:04]

PTAL

[tandrii(chromium), 2015-02-12 17:13:26]

LGTM

I agree with reasoning. Let's go ahead with this one.

[Michael Achenbach, 2015-02-12 18:33:44]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-02-12 18:34:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/914973002/1

[commit-bot: I haz the power, 2015-02-12 18:34:28]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-12 18:34:43]

Patchset 1 (id:??) landed as
https://crrev.com/44bc8646c3316ef75f00be9c404eccf6ca586505
Cr-Commit-Position: refs/heads/master@{#26629}

[agable, 2015-02-26 22:01:45]

I'm not particularly opposed to this -- obviously if you want to have a bunch of
extra branches in refs/heads that's fine since I don't spend much time the the
repo :) -- but I'm curious as to why it's required.

A chromium checkout that is pulling v8 via DEPS will fetch whatever hash or ref
is specified in the DEPS file. It shouldn't matter if it's in refs/heads or
elsewhere.

A chromium checkout that wants to deal directly with release branches can run
"fetch chromium --with-branch-heads", and it should get branch-heads from
chromium and all dependencies thereof, including v8.

So what exactly necessitated this? Is there something else infra could be doing
differently to not require polluting refs/heads?

[Michael Achenbach, 2015-02-28 14:33:15]

> A chromium checkout that is pulling v8 via DEPS will fetch whatever hash or
ref
> is specified in the DEPS file. It shouldn't matter if it's in refs/heads or
> elsewhere.

This simply doesn't work. I have no idea why. I explained a few cases in a
recent email thread that included you with the title "Fetching a DEPS revision
that's in branch-heads"

Here was a trial CL - by now the logs are gone, but I can submit a new one.
https://codereview.chromium.org/893633002/

This didn't even work in a local checkout of chromium, changing the DEPS and
then calling gclient sync.