Let release scripts determine version based on tags.

Let release scripts determine version based on tags.

Also create new v8 versions based on the roll ref, which
has some more verification steps than the candidate ref.

Improve bailout regarding existing versions. Only create a
new version if the revisions is in the future.

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

Committed: https://crrev.com/c071f4fbb68a8ecafa767ca5ca6f1e2c248f18cf
Cr-Commit-Position: refs/heads/master@{#26303}

[Michael Achenbach, 2015-01-27 11:31:11]

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

[Michael Achenbach, 2015-01-27 11:39:04]

PTAL

https://codereview.chromium.org/878913002/diff/1/tools/release/common_include...
File tools/release/common_includes.py (left):

https://codereview.chromium.org/878913002/diff/1/tools/release/common_include...
tools/release/common_includes.py:602: if len(version_parts) == 3:
This was a mistake. The version is used to later checkout based on it. 
Therefore it needs to match the tag.

https://codereview.chromium.org/878913002/diff/1/tools/release/common_include...
File tools/release/common_includes.py (right):

https://codereview.chromium.org/878913002/diff/1/tools/release/common_include...
tools/release/common_includes.py:48: CHANGELOG_FILE = "ChangeLog"
This was moved from push_to_candidates.

https://codereview.chromium.org/878913002/diff/1/tools/release/push_to_candid...
File tools/release/push_to_candidates.py (left):

https://codereview.chromium.org/878913002/diff/1/tools/release/push_to_candid...
tools/release/push_to_candidates.py:82: # Print assumed commit, circumventing
git's pager.
This interaction was never used -> remove.

[tandrii(chromium), 2015-01-28 00:07:48]

lgtm

[Michael Achenbach, 2015-01-28 10:08:31]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-01-28 10:08:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/878913002/20001

[commit-bot: I haz the power, 2015-01-28 10:09:01]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-01-28 10:09:12]

Patchset 2 (id:??) landed as
https://crrev.com/c071f4fbb68a8ecafa767ca5ca6f1e2c248f18cf
Cr-Commit-Position: refs/heads/master@{#26303}