Transfer notes when rebasing

Transfer notes when rebasing

[Francis Moreau]

Hello,

When rebasing a branch which contains commits with notes onto another
branch it happens that some commits are already presents in the target
branch.

In that case git-rebase correctly drops those (already present)
commits but it also drops the notes associated with them.

Can the notes be transfered somehow in the target branch on the
already present commits ?

Thanks
-- 
Francis

Re: Transfer notes when rebasing

[Jeff King]

On Wed, Sep 04, 2013 at 09:51:26AM +0200, Francis Moreau wrote:

> When rebasing a branch which contains commits with notes onto another
> branch it happens that some commits are already presents in the target
> branch.
> 
> In that case git-rebase correctly drops those (already present)
> commits but it also drops the notes associated with them.
> 
> Can the notes be transfered somehow in the target branch on the
> already present commits ?

Yes, see the notes.rewriteRef config option to enable this.

-Peff

Re: Transfer notes when rebasing

[John Keeping]

On Wed, Sep 04, 2013 at 03:53:10AM -0400, Jeff King wrote:
> On Wed, Sep 04, 2013 at 09:51:26AM +0200, Francis Moreau wrote:
> 
> > When rebasing a branch which contains commits with notes onto another
> > branch it happens that some commits are already presents in the target
> > branch.
> > 
> > In that case git-rebase correctly drops those (already present)
> > commits but it also drops the notes associated with them.
> > 
> > Can the notes be transfered somehow in the target branch on the
> > already present commits ?
> 
> Yes, see the notes.rewriteRef config option to enable this.

Does that actually work for this case?  It sounds like Francis has the
notes copying correctly when commits are rewritten but the notes are not
copied anywhere if the commit becomes empty.

I suspect it is difficult to do that in general as there is no clear way
to know which commit those notes should be copied to.

Re: Transfer notes when rebasing

[Francis Moreau]

On Wed, Sep 4, 2013 at 9:59 AM, John Keeping <john@keeping.me.uk> wrote:
> On Wed, Sep 04, 2013 at 03:53:10AM -0400, Jeff King wrote:
>> On Wed, Sep 04, 2013 at 09:51:26AM +0200, Francis Moreau wrote:
>>
>> > When rebasing a branch which contains commits with notes onto another
>> > branch it happens that some commits are already presents in the target
>> > branch.
>> >
>> > In that case git-rebase correctly drops those (already present)
>> > commits but it also drops the notes associated with them.
>> >
>> > Can the notes be transfered somehow in the target branch on the
>> > already present commits ?
>>
>> Yes, see the notes.rewriteRef config option to enable this.
>
> Does that actually work for this case?  It sounds like Francis has the
> notes copying correctly when commits are rewritten but the notes are not
> copied anywhere if the commit becomes empty.

I don't think so:

$ git config -l
...
notes.rewriteref=refs/notes/*

$ git notes show
note 1

$ git checkout -b target master~1
Switched to a new branch 'target'

$ git cherry-pick -x master
[target 93740ff] commit 6 (cherry picked from commit
5dc90209d7c0195dd9d671c234c49c903b9e1b10)
 1 file changed, 1 insertion(+)

$ git rebase target master
First, rewinding head to replay your work on top of it...

$ git notes show
error: No note found for object 93740ff96b37b2ed7aa0a78861c8beb87fdad474.

Thanks
-- 
Francis

Re: Transfer notes when rebasing

[Jeff King]

On Wed, Sep 04, 2013 at 08:59:41AM +0100, John Keeping wrote:

> On Wed, Sep 04, 2013 at 03:53:10AM -0400, Jeff King wrote:
> > On Wed, Sep 04, 2013 at 09:51:26AM +0200, Francis Moreau wrote:
> > 
> > > When rebasing a branch which contains commits with notes onto another
> > > branch it happens that some commits are already presents in the target
> > > branch.
> > > 
> > > In that case git-rebase correctly drops those (already present)
> > > commits but it also drops the notes associated with them.
> > > 
> > > Can the notes be transfered somehow in the target branch on the
> > > already present commits ?
> > 
> > Yes, see the notes.rewriteRef config option to enable this.
> 
> Does that actually work for this case?  It sounds like Francis has the
> notes copying correctly when commits are rewritten but the notes are not
> copied anywhere if the commit becomes empty.

Ah, I misunderstood. If we are dropping commits from the rebase because
their counterpart is already applied upstream, then no, there isn't an
automatic way to do this.

If the commits are dropped because a commit with the same patch-id
already exists upstream, you could match them up by patch-id and copy
the notes. Annoyingly, while we have things like "log --cherry-mark" to
show which commits are already present on each side, I do not think
there is a way to correlate them commit for commit. So I think you are
stuck doing something in the shell like:

  patch_ids() {
    git rev-list "$1" |
    git diff-tree --stdin -p |
    git patch-id |
    sort
  }

  patch_ids $upstream..HEAD >us
  patch_ids HEAD..$upstream >them

  join us them |
  cut -d' ' -f2-3 |
  git notes copy --stdin

However, if the commit is dropped because we find while applying that it
becomes empty, there is not much we can do. It may have been obsoleted
by its counterpart patch that had a different patch-id, or it may even
have been obsoleted by unrelated patches. In the latter case, there is
nothing to copy to. In the former, you would have to trying to match up
the commit messages or similar to guess that the two commits correspond.

-Peff

Re: Transfer notes when rebasing

[Francis Moreau]

On Wed, Sep 4, 2013 at 10:28 AM, Jeff King <peff@peff.net> wrote:
> On Wed, Sep 04, 2013 at 08:59:41AM +0100, John Keeping wrote:
>
>> On Wed, Sep 04, 2013 at 03:53:10AM -0400, Jeff King wrote:
>> > On Wed, Sep 04, 2013 at 09:51:26AM +0200, Francis Moreau wrote:
>> >
>> > > When rebasing a branch which contains commits with notes onto another
>> > > branch it happens that some commits are already presents in the target
>> > > branch.
>> > >
>> > > In that case git-rebase correctly drops those (already present)
>> > > commits but it also drops the notes associated with them.
>> > >
>> > > Can the notes be transfered somehow in the target branch on the
>> > > already present commits ?
>> >
>> > Yes, see the notes.rewriteRef config option to enable this.
>>
>> Does that actually work for this case?  It sounds like Francis has the
>> notes copying correctly when commits are rewritten but the notes are not
>> copied anywhere if the commit becomes empty.
>
> Ah, I misunderstood. If we are dropping commits from the rebase because
> their counterpart is already applied upstream, then no, there isn't an
> automatic way to do this.
>
> If the commits are dropped because a commit with the same patch-id
> already exists upstream, you could match them up by patch-id and copy
> the notes. Annoyingly, while we have things like "log --cherry-mark" to
> show which commits are already present on each side, I do not think
> there is a way to correlate them commit for commit. So I think you are
> stuck doing something in the shell like:
>
>   patch_ids() {
>     git rev-list "$1" |
>     git diff-tree --stdin -p |
>     git patch-id |
>     sort
>   }
>
>   patch_ids $upstream..HEAD >us
>   patch_ids HEAD..$upstream >them
>
>   join us them |
>   cut -d' ' -f2-3 |
>   git notes copy --stdin
>
> However, if the commit is dropped because we find while applying that it
> becomes empty, there is not much we can do. It may have been obsoleted
> by its counterpart patch that had a different patch-id, or it may even
> have been obsoleted by unrelated patches. In the latter case, there is
> nothing to copy to. In the former, you would have to trying to match up
> the commit messages or similar to guess that the two commits correspond.

Can't git-rebase at least handle the case where a patch and its
counterpart have the same patch-id ?

Also maybe git-rebase should warn when dropping a commit having a note
to tell the user that the note is dropped too.

-- 
Francis

Re: Transfer notes when rebasing

[Jeff King]

On Wed, Sep 04, 2013 at 10:47:22AM +0200, Francis Moreau wrote:

> > However, if the commit is dropped because we find while applying that it
> > becomes empty, there is not much we can do. It may have been obsoleted
> > by its counterpart patch that had a different patch-id, or it may even
> > have been obsoleted by unrelated patches. In the latter case, there is
> > nothing to copy to. In the former, you would have to trying to match up
> > the commit messages or similar to guess that the two commits correspond.
> 
> Can't git-rebase at least handle the case where a patch and its
> counterpart have the same patch-id ?

Certainly it could. My point was only that it doesn't currently (and it
does not even know what the counterpart is, only that there is one).

> Also maybe git-rebase should warn when dropping a commit having a note
> to tell the user that the note is dropped too.

That might end up annoying, depending on what you use notes for. But
I think if it were restricted to notes that would be rewritten via
notes.rewriteRef, it probably makes sense.

Patches welcome.

-Peff