From: Johan Herland <johan@herland.net>
To: Junio C Hamano <gitster@pobox.com>
Cc: David Turner <dturner@twopensource.com>,
Git mailing list <git@vger.kernel.org>,
Michael Haggerty <mhagger@alum.mit.edu>,
Eric Sunshine <sunshine@sunshineco.com>,
Philip Oakley <philipoakley@iee.org>
Subject: Re: [PATCH v3 2/6] notes: replace pseudorefs with real refs
Date: Wed, 29 Jul 2015 04:34:14 +0200 [thread overview]
Message-ID: <CALKQrge31G7-Ng8kZmy8=MgB+WQ3-bKimxCxOHOOwUMDuvRBzA@mail.gmail.com> (raw)
In-Reply-To: <xmqqlhdzby5o.fsf@gitster.dls.corp.google.com>
On Wed, Jul 29, 2015 at 2:33 AM, Junio C Hamano <gitster@pobox.com> 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:
>> ...
>> This is not the case for notes merges. If I start a notes merge from
>> worktree A, there is no "occupation" of that worktree. Before the
>> notes merge is resolved, I can do whatever I want in worktree A
>> (including checking out a different branch, performing a rebase,
>> whatever...). Instead, the notes merge creates its own worktree (that
>> is "occupied" until the notes merge is completed), which is completely
>> unrelated to worktree A.
>
> That does not mean the notes merge that you started when you were
> sitting in worktree A has to be shared with worktree B, by say doing
> "vi .git/NOTES_MERGE_WORKTREE/$commit && git notes merge --commit".
>
> Also the above does not explain why it is sensible for you to forbid
> worktree B from doing an unrelated notes merge of a different ref
> under refs/notes/* while your worktree A is doing a notes merge.
I do not argue that it is sensible to forbid concurrent unrelated
notes merges. I argue that using linked worktrees is a poor solution
for concurrent unrelated notes merges.
A better solution does not concern itself with worktrees at all, and
does not need to add nonsensical conditions like:
die_if_checked_out("NOTES_MERGE_REF", default_notes_ref());
A better solution does not need to add complexity to the branch or
linked worktree code to deal with notes merges. Instead, it simply
organizes the notes merge worktrees in such a manner that the correct
semantics naturally emerge.
Again, let's compare the two approaches (against the current situation):
Current situation:
- A single $GIT_COMMON_DIR/NOTES_MERGE_*
- Concurrent (unrelated or not) notes merges are simply not supported
Proposal A (please correct me where I have misunderstood what's proposed):
- Each worktree has its own $GIT_DIR/NOTES_MERGE_*
- Concurrent unrelated notes merges are supported, provided that you
create an additional linked worktree to "host" each concurrent notes
merge.
- Logic must be added to ensure unrelated-ness, i.e. make sure that
the NOTES_MERGE_REF in worktree X is different from all other
worktrees' NOTES_MERGE_REF.
Proposal B:
- The repo has a $GIT_COMMON_DIR/notes-merge/$ref/* hierarchy for
organizing concurrent notes merges
- Concurrent unrelated notes merges are supported, independently of
whether you have zero, one, or several worktrees.
- The notes merge code must be adjusted to work with the above
hierarchy, and must naturally fail if the user attempts to start a new
notes merge that would clobber an in-progress notes merge (only notes
merges to the same notes ref will clobber).
I obviously feel proposal B is superior to A, so I wonder what I have
missed about A that makes it preferable.
>> In principle, I agree that an ongoing notes-merge into
>> refs/notes/someotherthing should be able to coexist with an ongoing
>> notes-merge into refs/notes/commits. However, it does not make sense
>> to bind those notes-merges to a specific worktree.
>
> The thing is, the choice is between per worktree or per repository.
> Taking the latter would mean you can only be doing one notes merge
> at a time, even though you prepared multiple worktrees so that you
> can work on different things at a time. It is true that there is
> nothing inherent that ties a note merge to a worktree (a worktree is
> tied to a branch that is checed out, and there is no tie between a
> branch and a notes tree), but "not inherantly tied to" does not
> automatically mean "has to be one per repository". You'd ideally
> want to allow N workspaces for N refs/notes/* refs.
>
> But people work in worktrees, and that is their unit of working
> space. From that point of view, unless you are proposing a
> completely different design where the primary worktree can be used
> only for manipulating notes (hence, you can have worktrees for
> resolving refs/notes/A and refs/notes/B, in addition to the other
> worktrees you use to advance branches), treating NOTES_MERGE_REF as
> a per-worktree entity just like HEAD and the index is, would be the
> most sensible comporise.
I believe it is a bad compromise. It complicates the code, and it
provides a concurrent notes merges that is unnecessarily tied to (and
dependent on) worktrees. For example, if I wanted to perform N
concurrent notes merges in a project that happens to have a huge
worktree, I would now have to create N copies of the huge worktree...
...Johan
--
Johan Herland, <johan@herland.net>
www.herland.net
next prev parent reply other threads:[~2015-07-29 2:34 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-07-28 18:12 [PATCH v3 0/6] pseudorefs David Turner
2015-07-28 18:12 ` [PATCH v3 1/6] refs: Introduce pseudoref and per-worktree ref concepts David Turner
2015-07-28 18:12 ` [PATCH v3 2/6] notes: replace pseudorefs with real refs David Turner
2015-07-28 19:00 ` Junio C Hamano
2015-07-28 19:24 ` David Turner
2015-07-28 19:44 ` Junio C Hamano
2015-07-28 21:23 ` [PATCH] notes: handle multiple worktrees David Turner
2015-07-28 21:42 ` David Turner
2015-07-28 22:00 ` Junio C Hamano
2015-07-28 22:12 ` Junio C Hamano
2015-07-28 22:50 ` Johan Herland
2015-08-03 13:27 ` Duy Nguyen
2015-07-28 22:17 ` Eric Sunshine
2015-07-28 22:38 ` [PATCH v3 2/6] notes: replace pseudorefs with real refs Johan Herland
2015-07-28 22:52 ` Junio C Hamano
2015-07-28 23:43 ` Johan Herland
2015-07-29 0:33 ` Junio C Hamano
2015-07-29 0:56 ` Michael Haggerty
2015-07-29 1:23 ` Jacob Keller
2015-07-29 1:24 ` Johan Herland
2015-07-29 2:25 ` Junio C Hamano
2015-07-29 2:00 ` Junio C Hamano
2015-07-29 2:53 ` Johan Herland
2015-07-29 5:00 ` Junio C Hamano
2015-07-29 2:34 ` Johan Herland [this message]
2015-07-29 5:01 ` Junio C Hamano
2015-07-29 13:19 ` Johan Herland
2015-07-29 16:37 ` Junio C Hamano
2015-07-29 16:58 ` Junio C Hamano
2015-07-30 6:05 ` Johan Herland
2015-07-30 16:24 ` Junio C Hamano
2015-07-29 2:17 ` Junio C Hamano
2015-07-29 2:37 ` Johan Herland
2015-07-28 18:12 ` [PATCH v3 3/6] refs: add ref_type function David Turner
2015-07-29 6:32 ` Eric Sunshine
2015-07-28 18:12 ` [PATCH v3 4/6] pseudorefs: create and use pseudoref update and delete functions David Turner
2015-07-29 6:38 ` Eric Sunshine
2015-07-28 18:12 ` [PATCH v3 5/6] rebase: use update_ref David Turner
2015-07-28 18:12 ` [PATCH v3 6/6] sequencer: replace write_cherry_pick_head with update_ref David Turner
2015-07-28 19:01 ` [PATCH v3 0/6] pseudorefs Junio C Hamano
2015-07-28 19:07 ` David Turner
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