Partially reland Auto-generate v8 version based on tags.

Partially reland Auto-generate v8 version based on tags.

This relands parts of
https://codereview.chromium.org/843913009

It prepares for using this script outside of v8, e.g. in a
chromium hook.

The script is intended to run as a hook and will create
version_gen.cc if the content has changed.

Changes to gyp and gn files can land as a follow up, once
calling the hook on the chromium side has landed.

BUG=chromium:446166
LOG=n

Committed: https://crrev.com/0707afc863e14ad216fa2157f41fc35f86bd64b2
Cr-Commit-Position: refs/heads/master@{#26144}

[Michael Achenbach, 2015-01-19 13:16:51]

machenbach@chromium.org changed reviewers:
+ jkummerow@chromium.org, jochen@chromium.org, tandrii@chromium.org

[Michael Achenbach, 2015-01-19 13:20:02]

Patchset #2 (id:20001) has been deleted

[Michael Achenbach, 2015-01-19 15:15:23]

PTAL

[Michael Achenbach, 2015-01-19 15:18:45]

CC torne

[Jakob Kummerow, 2015-01-19 15:26:52]

lgtm

https://codereview.chromium.org/830093003/diff/80001/Makefile
File Makefile (right):

https://codereview.chromium.org/830093003/diff/80001/Makefile#newcode285
Makefile:285: version:
Please add "version" to the .PHONY list above

https://codereview.chromium.org/830093003/diff/80001/Makefile#newcode286
Makefile:286: build/generate_version.py
This is indented with tab, right? Codereview doesn't highlight it for some
reason.

[Michael Achenbach, 2015-01-19 15:48:08]

https://codereview.chromium.org/830093003/diff/80001/Makefile
File Makefile (right):

https://codereview.chromium.org/830093003/diff/80001/Makefile#newcode285
Makefile:285: version:
On 2015/01/19 15:26:52, Jakob wrote:
> Please add "version" to the .PHONY list above

Done.

https://codereview.chromium.org/830093003/diff/80001/Makefile#newcode286
Makefile:286: build/generate_version.py
On 2015/01/19 15:26:52, Jakob wrote:
> This is indented with tab, right? Codereview doesn't highlight it for some
> reason.

Yes. If you click on the raw changes view you can see the tab.

[Michael Achenbach, 2015-01-19 15:49:34]

The CQ bit was checked by machenbach@chromium.org

[commit-bot: I haz the power, 2015-01-19 15:50:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/830093003/100001

[commit-bot: I haz the power, 2015-01-19 16:23:30]

Committed patchset #5 (id:100001)

[commit-bot: I haz the power, 2015-01-19 16:23:44]

Patchset 5 (id:??) landed as
https://crrev.com/0707afc863e14ad216fa2157f41fc35f86bd64b2
Cr-Commit-Position: refs/heads/master@{#26144}