[PATCH 2/5] dim: auto-commit in apply-pull if rerere solved it all

[Daniel Vetter]

On Fri, May 4, 2018 at 9:39 PM, Dave Airlie <airlied at gmail.com> wrote:
> On 5 May 2018 at 00:10, Jani Nikula <jani.nikula at linux.intel.com> wrote:
>> On Fri, 04 May 2018, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>>> Now that we experiment with dim for drm-next it's much more likely
>>> that pull requests have conflicts. But also that dim already knows
>>> about them, in the recent drm-intel-next pull it resolve 7/8
>>> conflicts.
>>
>> I'll bet rerere will be really appealing for Dave. But until now we've
>> been able to shrug off potential bogus conflict resolutions with the
>> thought that it's just for drm-tip and not for real. Now it'll be for
>> real. *gasp*.
>
> Yeah I do have this worry myself, I spend a lot of time with git log, blame
> on every conflict I get to make sure I can definitely say I tried to
> understand it,
> I have to trust that others are going to put this sort of effort in,
> esp for drivers
> that aren't theirs.

One upshot of reusing conflict resulutions is at least for i915 our CI
will have tested it fully. We pre-merge test all the patches (except
when fools like me screw it up), I think merge resolutions should be
tested too before becoming part of permanent history.

I think the bigger issue is when there's conflicts outside of i915 or
core code used by i915, since that's not all that well-tested really.
In the past we've mostly gotten those in through forwarding your
drm-next or drm-fixes trees in drm-tip (since we don't backmerge
directly from Linus' tree, that's where new stuff by other drivers
first shows up). As long as you use dim to push drm-next it'll be you
who'll do the merge resolution in drm-tip, but with the upside that
you can get it tested before it's baked into a permanent merge.

Ideally we'd get everyone with a CI (AMD hopefully soon too) to test
drm-tip to make sure the preliminary merges are actually good. Once we
have that I think reusing the stored conflict resolutions is actually
good.

Aside: Everyone once in a while someone pushes a broken merge
resolution to drm-tip. If that happens all you need to do is revert
the offending commit from the drm-rerere branch (or multiple, if there
are) and the stored conflict should be gone from all places git can
get at it (in the past you had to run a special dim revert cmd, but we
reworked how the drm-rerere branch works to make this simpler).
Running dim rebuild-tip will then show you the conflict again, and you
can try another stab at it.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch