Re: [PATCH v3 6/6] worktree: copy sparse-checkout patterns and config on add

From: Elijah Newren <newren@gmail.com>
Date: Dec 29, 2021, 22:45 UTC
Message-ID: <CABPp-BFdVPRgFy8DLFEB13Trh5J4S+xma-U5FUnUvQLNMfNNjA@mail.gmail.com>
In-Reply-To: <0aa32f4d-9101-16ff-58b8-29a8651a69f8@gmail.com>

On Wed, Dec 29, 2021 at 1:39 PM Derrick Stolee <stolee@gmail.com> wrote:

Show 44 quoted lines

>
> On 12/29/2021 2:51 PM, Elijah Newren wrote:
> > On Wed, Dec 29, 2021 at 9:31 AM Derrick Stolee <stolee@gmail.com> wrote:
> >>
> >> On 12/29/2021 1:37 AM, Eric Sunshine wrote:
> >>> On Tue, Dec 28, 2021 at 4:32 PM Derrick Stolee via GitGitGadget
> >>> <gitgitgadget@gmail.com> wrote:
> >
> >>> The obvious way to work around this problem is to (again) special-case
> >>> `core.bare` and `core.worktree` to remove them when copying the
> >>> worktree-specific configuration. Whether or not that is the best
> >>> solution or even desirable is a different question. (I haven't thought
> >>> it through enough to have an opinion.)
> >>
> >> It makes sense to special case these two settings since we want to
> >> allow creating a working worktree from a bare repo, even if it has
> >> worktree config stating that it is bare.
> >
> > Agreed.
> >
> >> As far as the implementation goes, we could do the copy and then
> >> unset those two values in the new file. That's an easy enough change.
> >
> >> I'll wait for more feedback on the overall ideas (and names of things
> >> like the init-worktree-config subcommand).
> >
> > What value does the init-worktree-config subcommand provide; why
> > shouldn't we just get rid of it?
> >
> > I know Eric was strongly suggesting it, but he was thinking in terms
> > of always doing that full switchover step, or never doing it.  Both
> > extremes had the potential to cause user-visible bugs, and thus he
> > suggested providing a command to allow users to pick their poison.  I
> > provided a suggestion avoiding both extremes that doesn't have that
> > pick-your-poison approach, so I don't see why forcing users into this
> > extra step makes any sense.
> >
> > But perhaps I missed something.  Is there a usecase for users to
> > explicitly use this?
>
> I think the motivation is that worktree config is something that is
> harder to set up than to just run a 'git config' command, and we
> should guide users into a best practice for using it. The
> documentation becomes "run this command to enable it".

Okay, but that's an answer to a different question -- namely, "if users want/need to explicitly set it up, why should we have a command?" Your answer here is a very good answer to that question, but you've assumed the "if". My question was on the "if": (Why) Do users need or want to explicitly set it up?

Secondarily, if users want to set it up explicitly, is the work here really sufficient to help guide them? In particular, I discovered and started using extensions.worktreeConfig without ever looking at the relevant portions of git-worktree.txt (the references in git-config.txt never mentioned them). I also pushed this usage to others, including even to you with `git-sparse-checkout`, and no reviewer on this list ever caught it or informed me of the `proper` additional guidelines found in git-worktree.txt until this thread started. So, relying on folks to read git-worktree.txt for this config item feels a bit weak to me. Granted, your new command will be much more likely to be read since it appears near the top of git-worktree.txt, but I just don't think that's enough. The references to extensions.worktreeConfig in git-config.txt should reference any special command or extended steps if we expect users to manually configure it (whether via explicit new subcommand or via also playing with other config settings).

Anyway, if we think users want to set it up explicitly, and we address
the discoverability problem above, then I'd vote for
"independent-config" or "private-config" (or _maybe_
"migrate-config").  Because:
  * no sense repeating the word `worktree` in `git worktree
init-worktree-config`.  It's redundant.
  * The words "independent" or "private" suggest what it does and why
users might want to use the new subcommand.
  * It's not an "init":
    * The documentation makes no attempt to impose a temporal order of
using this command before `git worktree add`.  (Would we even want
to?)
    * As per my recommendation elsewhere, this step just isn't needed
for the vast majority of users (i.e. those with non-bare clones who
leave core.worktree alone).
    * ...and it's also not needed for other (core.bare=true or
core.worktree set) users since `git worktree add` will automatically
run this config migration for them

And, actually, with the name "independent-config" or "private-config", I might be answering my own question. It's a name that speaks to why users might want it, so my objection to the new command is rapidly diminishing.

> It also provides a place to update the steps if we were to change
> something in the future around worktree config, but I'm guessing
> the ship has sailed and backwards compatibility will keep us from
> introducing a new setting that would need to be added here.

Yeah, the best time to force a config change is probably when we introduce a new command with it. If we had forced core.repositoryFormatVersion=1 in order to read extensions.* at the time that extensions.* was introduced, that would have been fine (When we tried it later, we had to revert it for backward compatibility reasons.). If we had forced extensions.worktreeConfig=true when introducing git-worktree, that would have been fine. We did force extensions.worktreeConfig=true when we introduced git-sparse-checkout, which was good, though we localized it to sparse-checkout and avoided adding it to worktree usage in general at that point.

The other good time to force a config change is when we have cases where behavior is already broken anyway. For example, the (core.bare=true or core.worktree is set) case that started this thread. But in such cases, we have to localize the forced-config change to the cases that are "broken anyway" unless we can verify it won't break other cases.

I'm not sure that this new subcommand will ever fall into either of these categories, so I also agree that we'll be unlikely to ever change it.