DEPS hook for installing the clang-format merge driver.

DEPS hook for installing the clang-format merge driver.

This hook automatically installs and maintains a merge tool config for
the clang-format merge driver, which can help automatically resolve
conflicts that arise from clang-format reformatting patches.

Note that this change does not have any impact other than tweaking the
git config of the main project). The custom merge driver will later be
activated by updating .gitattributes with lines like:

*.cpp   merge=clang-format
*.h     merge=clang-format

BUG=574611
Committed: https://crrev.com/3db0d1dfa2532a7c7380f9c15deef1c3fe0139e5
Cr-Commit-Position: refs/heads/master@{#420704}

[dcheng, 2016-09-22 07:52:37]

dcheng@chromium.org changed reviewers:
+ thakis@chromium.org

[dcheng, 2016-09-22 07:52:37]

Split off from https://codereview.chromium.org/2356933002/ and incorporated as a
DEPS hook instead. Note that I left the actual merge driver in depot_tools,
since it's currently using the convenient clang_format helpers to find the
clang-format binary.

I also haven't tested this on Mac/Windows yet (I will do so once I'm in the
office tomorrow)

[Nico, 2016-09-22 13:22:37]

https://codereview.chromium.org/2359933005/diff/20001/tools/clang_format_merg...
File tools/clang_format_merge_driver/install_git_hook.py (right):

https://codereview.chromium.org/2359933005/diff/20001/tools/clang_format_merg...
tools/clang_format_merge_driver/install_git_hook.py:23: print 'Skipping...'
this is probably fast enough that we could just unconditionally call `git
config` on every runhooks, then we don't need this versioning stuff.

Is it possible to write an absolute path for the driver path? Then the driver
could be in src/ too and we could write an absolute path to it. (And if we
config'd every runhooks, we'd even survive local repo moves as long as they're
followed by another runhook)

https://codereview.chromium.org/2359933005/diff/20001/tools/clang_format_merg...
tools/clang_format_merge_driver/install_git_hook.py:35: ['git', 'config',
'merge.clang-format.name', 'clang-format merge driver'])
Is the cwd for running hooks guaranteed? Does this do the right thing if you're
not in src/ when running runhooks?

[Nico, 2016-09-22 13:24:24]

but lgtm as-is too if you'd rather have the actual merge driver in depot_tools
– clang-format is there too.

[dcheng, 2016-09-22 17:08:53]

On 2016/09/22 13:24:24, Nico wrote:
> but lgtm as-is too if you'd rather have the actual merge driver in depot_tools
> – clang-format is there too.

I think it might be nice to keep it in there (just to make it easier to use the
correct clang-format binary), but let's see how the depot_tools owners feel
about that.

https://codereview.chromium.org/2359933005/diff/20001/tools/clang_format_merg...
File tools/clang_format_merge_driver/install_git_hook.py (right):

https://codereview.chromium.org/2359933005/diff/20001/tools/clang_format_merg...
tools/clang_format_merge_driver/install_git_hook.py:23: print 'Skipping...'
On 2016/09/22 13:22:37, Nico wrote:
> this is probably fast enough that we could just unconditionally call `git
> config` on every runhooks, then we don't need this versioning stuff.
> 
> Is it possible to write an absolute path for the driver path? Then the driver
> could be in src/ too and we could write an absolute path to it. (And if we
> config'd every runhooks, we'd even survive local repo moves as long as they're
> followed by another runhook)

Oops, I meant to remove this print anyway.

https://codereview.chromium.org/2359933005/diff/20001/tools/clang_format_merg...
tools/clang_format_merge_driver/install_git_hook.py:35: ['git', 'config',
'merge.clang-format.name', 'clang-format merge driver'])
On 2016/09/22 13:22:37, Nico wrote:
> Is the cwd for running hooks guaranteed? Does this do the right thing if
you're
> not in src/ when running runhooks?

That's why there's an os.chdir on line 16 =)

[Nico, 2016-09-23 15:27:55]

This can be cq+'d, yes?

[dcheng, 2016-09-23 16:12:06]

On 2016/09/23 15:27:55, Nico wrote:
> This can be cq+'d, yes?

I want to do a final test run on Windows, yesterday was mostly spent doing lots
of giant rebuilds on Windows so I didn't have an opportunity for testing.

[dcheng, 2016-09-23 18:01:28]

Alright, I fixed the Windows stuff and did more testing than GLaDOS. PTAL.

[Nico, 2016-09-23 18:05:35]

Nice patch set descriptions.

https://codereview.chromium.org/2359933005/diff/100001/tools/clang_format_mer...
File tools/clang_format_merge_driver/install_git_hook.py (right):

https://codereview.chromium.org/2359933005/diff/100001/tools/clang_format_mer...
tools/clang_format_merge_driver/install_git_hook.py:17: cmd.append('git.bat')
will this work on cygwin? (which seems like an argument for shell=True --
alternatively this could detect cygwin and reexec itself under cmd like
https://cs.chromium.org/chromium/tools/depot_tools/win_toolchain/get_toolchai...
but just shell=true on win is probably easier)

[dcheng, 2016-09-23 18:46:55]

https://codereview.chromium.org/2359933005/diff/100001/tools/clang_format_mer...
File tools/clang_format_merge_driver/install_git_hook.py (right):

https://codereview.chromium.org/2359933005/diff/100001/tools/clang_format_mer...
tools/clang_format_merge_driver/install_git_hook.py:17: cmd.append('git.bat')
On 2016/09/23 18:05:35, Nico wrote:
> will this work on cygwin? (which seems like an argument for shell=True --
> alternatively this could detect cygwin and reexec itself under cmd like
>
https://cs.chromium.org/chromium/tools/depot_tools/win_toolchain/get_toolchai...
> but just shell=true on win is probably easier)

sys.platform == 'cygwin' on cygwin, so it's no problem:
https://docs.python.org/2/library/sys.html

[Nico, 2016-09-23 18:48:13]

a'ight, lgtm :-)

[dcheng, 2016-09-23 18:49:28]

The CQ bit was checked by dcheng@chromium.org

[commit-bot: I haz the power, 2016-09-23 18:50:17]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-09-23 19:52:27]

Committed patchset #6 (id:100001)

[commit-bot: I haz the power, 2016-09-23 19:55:20]

Description was changed from

==========
DEPS hook for installing the clang-format merge driver.

This hook automatically installs and maintains a merge tool config for
the clang-format merge driver, which can help automatically resolve
conflicts that arise from clang-format reformatting patches.

Note that this change does not have any impact other than tweaking the
git config of the main project). The custom merge driver will later be
activated by updating .gitattributes with lines like:

*.cpp   merge=clang-format
*.h     merge=clang-format

BUG=574611
==========

to

==========
DEPS hook for installing the clang-format merge driver.

This hook automatically installs and maintains a merge tool config for
the clang-format merge driver, which can help automatically resolve
conflicts that arise from clang-format reformatting patches.

Note that this change does not have any impact other than tweaking the
git config of the main project). The custom merge driver will later be
activated by updating .gitattributes with lines like:

*.cpp   merge=clang-format
*.h     merge=clang-format

BUG=574611

Committed: https://crrev.com/3db0d1dfa2532a7c7380f9c15deef1c3fe0139e5
Cr-Commit-Position: refs/heads/master@{#420704}
==========

[commit-bot: I haz the power, 2016-09-23 19:55:21]

Patchset 6 (id:??) landed as
https://crrev.com/3db0d1dfa2532a7c7380f9c15deef1c3fe0139e5
Cr-Commit-Position: refs/heads/master@{#420704}