Re: Applying the same patch multiple times

[Kyle Meyer <kyle@kyleam.com>]

Ihor Radchenko writes:

> I also noticed one minor annoyance when I return to work on the
> previously applied patch.
>
> My starting point is the patch-containing email. Then, I run piem-am and
> use the default automatically generated branch.

Interesting, using the email as the staring point for jumping to a
branch isn't a use case that I've considered, but, yeah, I can see why
that's appealing.

> Expected behaviour: Silently switch to the already existing branch
> unless that branch had modifications to the patch in the email. In the
> latter case, either throw an error or show the changes interactively.

Hmm, this makes a strong assumption about the patch to branch name
mapping, but the branch name offered in the prompt is just a (hopefully
helpful) suggestion/starting point.

To implement this feature, I'm not seeing a way around needing to
maintain the mapping.  The first thing that comes to mind is that the
Git configuration for the branch could be a good place to keep it (say
branch.$branch.piem-mid).  That would allow generating the mid->branch
mapping for a coderepo and has the nice feature that it's cleaned up by
Git when the branch is deleted.  There are other wrinkles here, but I
think the overall approach would probably be workable.

> Observed behaviour: Because the branch already exists and the patch is
> already applied, git am throws an error.

Odd.  I expected the git-checkout call upstream of git-am to fail
(saying something like "fatal: a branch named 'blah' already exists").
Testing quickly, that's what I see on my end.

(Either way, that's of course not your desired behavior.)

> I think a more useful approach would be something like:
> 1. piem creates a throwaway branch and apply the patch in the email
> 2. piem rebases the existing branch onto that throwaway branch

I'm not quite connecting this (1)...

> That way, I can start working on a patch from email, possibly add some
> followup commits and still be able to return to this WIP branch starting
> from the patch email.

...to this (2).  2 more or less aligns with how I understood the rest of
your email, but I don't see where 1 comes in.  If you already applied a
patch from a particular message, that patch isn't changing, so wouldn't
you just want to jump to the associated branch, even if you amended the
given commit and/or added commits on top?

Perhaps the answer is that these are updated patches from later
messages.  I'd say those ought to land on a separate branch, though I
know that unfortunately some people aren't good about bumping the reroll
count of their patches, in which case the suggested branch name won't be
different.

Thanks for your feedback.