Re: [PATCH v3 2/6] notes: replace pseudorefs with real refs

[Johan Herland <johan@herland.net>]

On Wed, Jul 29, 2015 at 2:56 AM, Michael Haggerty <mhagger@alum.mit.edu> wrote:
> Johan Herland <johan@herland.net> writes:
>> Here is where we start to differ. I would say that starting a notes
>> merge is completely unrelated to your worktree. Consider this:
>
> It sounds like what a notes merge really wants is a new linked worktree
> that has branch refs/notes/foo checked out:

Yes, almost. There are some complications with the concept of
"checking out" a notes tree:

 - The notes tree fanout must be flattened (so that when merging two
note trees with different fanout, conflicting notes (e.g. deadbeef...
and de/adbeef....) are turned into a file-level conflict in the notes
merge worktree (i.e. contents with conflict markers in
.git/NOTES_MERGE_WORKTREE/deadbeef...).

 - Notes trees may be very large (e.g. one note per commit for the
entire project history), so we want to avoid checking out as many
notes as possible. Currently we only checkout the notes that actually
do conflict, and keep the rest referenced from NOTES_MERGE_PARTIAL.

> * This would allow multiple notes merges to take place at the same time
> provided they target different merge references.
>
> * This would prevent multiple notes merges to the same notes reference
> at the same time by the same mechanism that prevents the same branch
> from being checked out in two linked worktrees at the same time.
>
> It's just a thought; I have no idea whether it is practical...

I'm not sure whether it's worth trying to reuse the same linked
worktree mechanism for notes trees, when (a) the concept of "checking
out" a notes tree is so different, as explained above, and (b)
currently the only use case for a notes worktree is during a notes
merge.


...Johan

> Michael
>
> --
> Michael Haggerty
> mhagger@alum.mit.edu
>

-- 
Johan Herland, <johan@herland.net>
www.herland.net