Re: [PATCH v4] sparse-checkout.txt: new document with sparse-checkout directions

[ZheNing Hu <adlternative@gmail.com>]

Elijah Newren <newren@gmail.com> 于2023年1月20日周五 12:30写道：
>
> On Sat, Jan 14, 2023 at 2:19 AM ZheNing Hu <adlternative@gmail.com> wrote:
> >
> > Elijah Newren <newren@gmail.com> 于2022年11月16日周三 13:49写道：
> >
> > > [...]
> > > > > +    The fact that files can move between the 'tracked' and 'untracked'
> > > > > +    categories means some commands will have to treat untracked files
> > > > > +    differently.  But if we have to treat untracked files differently,
> > > > > +    then additional commands may also need changes:
> > > > > +
> > > > > +      * status
> > > > > +      * clean
> > > > > +
> > > >
> > > > I'm a bit worried about git status, because it's used in many shells
> > > > (e.g. zsh) i
> > > > in the git prompt function. Its default behavior is restricted, otherwise users
> > > > may get blocked when they use zsh to cd to that directory. I don't know how
> > > > to reproduce this problem (since the scenario is built on checkout to a local
> > > > unborn branch).
> > >
> > > Could you elaborate?  I'm not sure if you are talking about an
> > > existing problem that you are worried about being exacerbated, or a
> > > hypothetical problem that could occur with changes.  Further, your
> > > wording is so vague about the problem, that I have no idea what its
> > > nature is or whether any changes to status would even possibly have
> > > any bearing on it.  But the suggested changes to git status are
> > > simply:
> > >
> >
> > I find this special case, it will fetch some blobs when "git status".
> > First, we init a git repository, then set sparse specification to "*.js" with
> > no-cone mode, then use blob:none filter to fetch all commits and trees,
> > and finally checkout to the default branch.
> >
> > #!/bin/sh
> >
> > rm -rf sparse-checkout-example
> > git init sparse-checkout-example
> > git -C sparse-checkout-example remote add origin
> > git@github.com:derrickstolee/sparse-checkout-example.git
> > git -C sparse-checkout-example sparse-checkout set --no-cone *.js
> > git -C sparse-checkout-example fetch origin --filter=blob:none main
> > git -C sparse-checkout-example branch --track main origin/main
> > git -C sparse-checkout-example checkout main
> >
> > Then let's do a git status, which some zsh git plugin
> > will do when user "cd" the git repository.
> >
> > # git -C sparse-checkout-exmaple status
> >
> > remote: Enumerating objects: 1, done.
> > remote: Total 1 (delta 0), reused 0 (delta 0), pack-reused 1
> > Receiving objects: 100% (1/1), 416 bytes | 416.00 KiB/s, done.
> > remote: Enumerating objects: 1, done.
> > remote: Total 1 (delta 0), reused 0 (delta 0), pack-reused 1
> > Receiving objects: 100% (1/1), 160 bytes | 160.00 KiB/s, done.
> > remote: Enumerating objects: 1, done.
> > remote: Total 1 (delta 0), reused 0 (delta 0), pack-reused 1
> > Receiving objects: 100% (1/1), 2.01 KiB | 2.01 MiB/s, done.
> > remote: Enumerating objects: 1, done.
> > remote: Total 1 (delta 0), reused 0 (delta 0), pack-reused 1
> > Receiving objects: 100% (1/1), 120 bytes | 120.00 KiB/s, done.
> > On branch main
> > Your branch is up to date with 'origin/main'.
> >
> > You are in a sparse checkout with 8% of tracked files present.
> >
> >
> > It took 17.00 seconds to enumerate untracked files. 'status -uno'
> > may speed it up, but you have to be careful not to forget to add
> > new files yourself (see 'git help status').
> > nothing to commit, working tree clean
> >
> > Yeah, here it fetches four blobs, and takes 17s!!!
> >
> > So what blobs are we fetching?
> >
> > GIT_TRACE_PACKET=1 git -C sparse-checkout-example status
> > ...
> > 18:02:32.989231 pkt-line.c:80           packet:        fetch> want
> > dff85a65c0ef4b50a4c01bdd4a247b974bc45f90
> > ...
> > 18:02:37.059203 pkt-line.c:80           packet:        fetch> want
> > f07ead02d13f62414589b1f1b891bb6a764ec91f
> > ...
> > 18:02:40.868899 pkt-line.c:80           packet:        fetch> want
> > 3c4efe206bd0e7230ad0ae8396a3c883c8207906
> > ...
> > 18:02:44.961809 pkt-line.c:80           packet:        fetch> want
> > 6590681af7e177dc71fe08648c4bbf4223b82866
> >
> >
> > Then let's we look what's the blob:
> > git log --find-object=dff85a65c0ef4b50a4c01bdd4a247b974bc45f90 --stat
> > commit 8ec229339caad56eb849c67361a9699004564177
> > Author: Derrick Stolee <dstolee@microsoft.com>
> > Date:   Mon Dec 30 13:30:27 2019 -0500
> >
> >     Add twbs/bootstrap
> >
> >  web/browser/.gitignore | 47 +++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 47 insertions(+)
> >
> > git log --find-object=f07ead02d13f62414589b1f1b891bb6a764ec91f --stat
> > commit 9c5a31030de62355410a322923e33e90a00032f6
> > Author: Derrick Stolee <dstolee@microsoft.com>
> > Date:   Mon Dec 30 13:31:06 2019 -0500
> >
> >     Add artsy/artsy.github.io
> >
> >  web/editor/.gitignore | 13 +++++++++++++
> >  1 file changed, 13 insertions(+)
> >
> > Yeah, it seems that git status fetch these .gitigore files.
> > So what's the wrong here?
>
> Nothing; this looks exactly as I'd expect.
>
> `git status` is supposed to check whether untracked files are ignored
> or not, and it needs .gitignore files to do so.  If an entire
> directory is missing, then it can avoid loading a .gitignore under
> that directory, but you set up your patterns such that no directory is
> likely to be excluded.
>

This may be a bit strange, why doesn't the cone mode have this problem?

> Maybe there are other special cases that one could attempt to handle
> (e.g. first check if there are any untracked files in a directory and
> only then check for which are ignored, but that'd probably take some
> big refactoring of some hairy dir.c code to accomplish something like
> that, and you'd have to be really careful to not regress the
> performance of non-sparse cases).  Personally, I don't think it's
> worth it.  If you really don't like it, I'd suggest choosing any one
> of the following ways to avoid it:
>

This "bug" may not be very important, because it has no application
at present,  scalar also uses cone mode by default.

>   * Include the .gitignore files in your sparse-checkout; might as
> well since you're going to get them anyway.

This can also seem like a pain in the butt because of the extra
unnecessary .gitigore downloads.

>   * Set status.showUntrackedFiles to `no` so that .gitignore files are
> irrelevant

This may also be a temporary rather than a complete solution.

>   * Use cone mode instead of non-cone mode (and yes, restructure your
> repo if needed)

No, I might think cone mode has some other disadvantages: it includes
too many files. I would prefer to get the behavior of non-cone mode.

>   * Remove the .gitignore files and commit their deletion.  Just do
> without them, somehow.

That's not a proper solution absolutely.

Anyway, thanks for the answer!
--
ZheNing Hu