[OE-core] [PATCH] lib/oe/patch.py: Prefer "git am" over "git apply" when applying git patches

[Otavio Salvador]

On Mon, Jan 6, 2014 at 8:10 PM, Saul Wold <sgw at linux.intel.com> wrote:
> On 12/31/2013 06:18 AM, Laszlo Papp wrote:
>>
>> Ping?
>>
>> Alternatively, the system could also have an option for further
>> fine-tuning what to do with git patches
>>
>> On Tue, Dec 24, 2013 at 12:44 PM, Laszlo Papp <lpapp at kde.org> wrote:
>>>
>>> It is better to use "git am" when possible to preserve the commit
>>> messages and
>>> the mail format in general for patches when those are present. A typical
>>> use
>>> case is when developers would like to keep the changes on top of the
>>> latest
>>> upstream, and they may occasionally need to rebase. This is not possible
>>> with
>>> "git diff" and "diff" generated patches.
>>>
>>> Since this is not always the case, the fallback would be the "git apply"
>>> operation which is currently available.
>>>
> Looking at this, is it possible to detect a git patch and only then use git
> am?  Since most of the patches carried in oe-core and other layers the 'git
> am' will typically fail and increase the build time since it will have to
> re-run the git apply, we don't want to had more forking and work in the main
> hot path.
>
> I am not the expert in this, neither is RP, so maybe Chris can comment
> further.

I am not sure it'd buy us a lot trying to detect it; in fact using git
am patches easy rework, rebase and upstreaming of those.

To detect it, we'd need to parse the file somehow and I am unsure it
would be faster than just try to apply it.

My 2c.

-- 
Otavio Salvador                             O.S. Systems
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