Re: Todays git migration results

Alex Hunsaker <badalex(at)gmail(dot)com> writes:
> How exactly patches get applied into back branches? Has that been
> spelled out somewhere? There are a lot of ways to do it. For
> instance git.git seems to apply the patch to the earliest branch first
> and then merge it on up so that everything can share the same
> commit/hash. That looks like a royal PITA to me, and I assume the
> plan is to just cherry-pick commits back. As long as we use git
> cherry-pick -x, I agree with Magnus, it should be fairly easy to write
> a short script to do it. II'll even volunteer if the above is
> basically the only requirement :-).

There was discussion about that before, but I don't know whether we
really have a solution that will work comfortably. A couple of
comments:

* My practice has always been to develop a fix in HEAD first and then
work backwards. I'm going to resist any tool that tries to force me
to do it the other way. There are a couple of reasons for that: one,
I'm generally more familiar with HEAD, and two, I want HEAD to have the
cleanest solution. If you do an old branch first, you'll probably come
up with a solution that is good for that branch but could be improved
in newer ones, eg by using some subroutine or facility that doesn't
exist earlier. Forward-patching won't encourage you to find that.

* My experience is that a patch that has to go back more than one or two
branches is almost never exactly the same on each branch, even without
any of the non-trivial changes suggested above. We constantly do things
like rearrange the arguments of some function that's used everywhere.
So "patch" is definitely not smart enough to back-patch the fixes by
itself. Maybe git will be a lot smarter but I'm not expecting miracles.
Anything that is based on "same hash" is pretty much guaranteed to
not do what I need.

I'd be satisfied with a tool that merges commit reports if they have the
same log message and occur at approximately the same time, which is the
heuristic that cvs2cl uses.

regards, tom lane