Re: git MFC/cherry-pick question

On Thu, Jun 3, 2021 at 8:29 PM Alan Somers <asomers@freebsd.org> wrote:

> On Thu, Jun 3, 2021 at 8:13 PM Rick Macklem <rmacklem@uoguelph.ca> wrote:
>
> > Hi,
> >
> > I am trying to MFC a commit to stable/12.
> > The cherry-pick works, but the resultant code
> > is not correct and won't build.
> > --> I broke the build yesterday and manually
> >        reverted the breakage.
> >
> > So, how do I do this?
> >
> > Do I have to manually edit the file after the
> > cherry-pick and then do something like a
> > git commit -a
> > to get the edited change in, or is there a
> > way to tell it to add it to the cherry-pick or ??
> >
> > Thanks anyone, for help with this, rick
> >
>
> Is the resulting code incorrect because of a git merge error, or because
> stable/13 requires slightly different code than main?  If it's the latter,
> then after the "git cherry-pick", you should edit the file manually and do
> a "git commit -a --amend".  That will produce the right result.  You don't
> have to worry about screwing up merge history by using "--amend", because
> "git cherry-pick" already screws up merge history.  If your problem is the
> former, then the same solution will work, although you might be able to
> solve it by using some fancy git merge options instead.
>

git cherry-pick does not screw up merge history. The hashes of the diffs
are used
by git to know what's been merged and what hasn't. git commit --amend to fix
things up screws up this mechanism a bit. That's why we do the
'git cherry-pick -x' which records the hash as a backup.  git log
--cherry-pick can
help find changes to merge. There's been some scripts offered to also help
find things...

And usually when git cherry-pick doesn't produce working code, it's because
other things weren't cherry-pucked that the code depends on. Sometimes you
can
find the changes to cherry-pick it, other times you have to do a manual
fixup.

Warner