Re: [PATCH] ls-files: add %(skipworktree) atom to format option

[ZheNing Hu <adlternative@gmail.com>]

Elijah Newren <newren@gmail.com> 于2023年1月12日周四 18:00写道：
>
> On Wed, Jan 11, 2023 at 7:42 AM ZheNing Hu via GitGitGadget
> <gitgitgadget@gmail.com> wrote:
> >
> > From: ZheNing Hu <adlternative@gmail.com>
> >
> > Because sometimes we want to check if the files in the
> > index match the sparse specification by using
> > `git ls-files -t`, but `-t` option have semi-deprecated,
>
> Where `semi-deprecated` was explicitly "suggest other functionality in
> preference, but do not ever remove"[1].  The "suggest other
> functionality in preference" for "ls-files -t" came about because
> people got confused about staged files which have (a) no unstaged
> changes, vs. (b) unstaged content changes, vs. (c) unstaged deletion
> of the file.  Such users accidentally presumed that "H" (defined
> simply as "cached") should only refer to class (a) when it refers to
> the fact that the file is tracked (and not conflicted) and thus refers
> to any of (a), (b), and (c)[2].  (I wonder if changing the definition
> of "H" in the manual from "cached" to "tracked-and-not-conflicted"
> would fix this confusion.)  In contrast, comparing tracked vs.
> not-tracked-because-skip-worktree files, the distinction between "H"
> and "S" makes lots of sense and naturally you want "H" to represent
> all 3 of (a), (b), and (c).  So, for the skip-worktree bit usecase,
> "ls-files -t" doesn't cause the same confusion.  (Perhaps the fact
> that we have a tri-state of "M" (unmerged) vs "S" (skip-worktree) vs.
> "H" (all other tracked files) could cause minor confusion, but in
> practice the possibility of "M" just hasn't seemed to have caused
> issues for sparse-checkout users or scripts.)
>

OK, I probably understand that the '-t' "semi-deprecated" was caused
by the confusion of the 'H' semantics.

> Further, since sparse-checkouts and monorepos really started taking
> off 4-5 years ago, "git ls-files -t" has been used *heavily* (but
> mostly by low-level script things rather than user-facing UI).  If we
> wanted to come up with a better place to report on the skip-worktree
> bit and have scripts rely on that, we probably should have made such a
> change back then...if not another 8-9 years earlier.  At this point,
> "ls-files -t" simply cannot be removed, even if we wanted to.
>

Ah, It seems we can't go back so far :)

> [1] As per this quote from 5bc0e247c4 ("Document ls-files -t as
> semi-obsolete.", 2010-07-28):
>     "git ls-files -t" is [...] badly documented, hence we point the
>     users to superior alternatives.
>     The feature is marked as "semi-obsolete" but not "scheduled for removal"
>     since it's a plumbing command, scripts might use it, and Git testsuite
>     already uses it to test the state of the index.
> [2] https://lore.kernel.org/git/fcaeb9bf0908190204h31bc839ai39972a251040d449@mail.gmail.com/
> (a.k.a. gmane:126516 from the commit message referenced above)
>

It was good to discover that I had misunderstood the point:
"semi-obsolete" is not git want to remove `-t`.

> > So introduce "%(skipworktree)" atom to git ls-files
> > `--format` option.
>
> Given my above comments, I personally don't buy this as justification
> for adding a new way of reporting on the skip-worktree bit.  It may
> still make sense to add this feature or something like it, but I
> personally think it deserves separate justification from "`ls-files
> -t` is semi-deprecated".
>

Agree now.

> (Others, of course, may disagree with me, but if this is the only
> justification for this change, then I'm more likely to want to fix the
> ls-files manual to remove the "semi-deprecated" notice and fix the
> definition of "H" to be less misleading than to make a change like
> this.)
>
> > When we use this option, if the file
> > match the sparse specification and removed from working
> > tree...
>
> The "and removed from working tree" portion of this sentence is
> superfluous.  (And actually makes it harder to understand, I had to
> try to think through a bunch of cases to try to figure out why you
> might be trying to add some extra qualifier.)
>

I just quoted the definition of SKIP_WORKTREE from
Documentation/technical/sparse-checkout.txt:

    SKIP_WORKTREE: When tracked files do not match the sparse specification and
      are removed from the working tree, the file in the index is marked
      with a SKIP_WORKTREE bit.

> > ...it will output "yes", othewise, output "no".
>
> typo in "otherwise".
>
> Also, your commit message claims output different from what your code
> below implements and what your testcase shows.  ("yes"/"no" vs.
> "true"/"false")
>

Yeah, I would have said "true"/"false".

> > Signed-off-by: ZheNing Hu <adlternative@gmail.com>
> [...]
> > diff --git a/Documentation/git-ls-files.txt b/Documentation/git-ls-files.txt
> > index 440043cdb8e..0e50307121d 100644
> > --- a/Documentation/git-ls-files.txt
> > +++ b/Documentation/git-ls-files.txt
> > @@ -260,6 +260,12 @@ eolattr::
> >         that applies to the path.
> >  path::
> >         The pathname of the file which is recorded in the index.
> > +skipworktree::
> > +       If the file in the index marked with SKIP_WORKTREE bit.
> > +       It means the file do not match the sparse specification
> > +       and removed from working tree.
> > +       See link:technical/sparse-checkout.txt[sparse-checkout]
> > +       for more information.
>
> Should the actual wording be included here? (i.e. "yes"/"no",
> "true"/"false", or whatever you end up using)?
>

Yes, it will be better to mention its output.

> >  EXCLUDE PATTERNS
> >  ----------------
> > diff --git a/builtin/ls-files.c b/builtin/ls-files.c
> > index a03b559ecaa..d1a27f28f01 100644
> > --- a/builtin/ls-files.c
> > +++ b/builtin/ls-files.c
> > @@ -280,6 +280,9 @@ static size_t expand_show_index(struct strbuf *sb, const char *start,
> >                               data->pathname));
> >         else if (skip_prefix(start, "(path)", &p))
> >                 write_name_to_buf(sb, data->pathname);
> > +       else if (skip_prefix(start, "(skipworktree)", &p))
> > +               strbuf_addstr(sb, ce_skip_worktree(data->ce) ?
> > +                             "true" : "false");
> >         else
> >                 die(_("bad ls-files format: %%%.*s"), (int)len, start);
> >
> > diff --git a/t/t3013-ls-files-format.sh b/t/t3013-ls-files-format.sh
> > index efb7450bf1e..ac8b865c275 100755
> > --- a/t/t3013-ls-files-format.sh
> > +++ b/t/t3013-ls-files-format.sh
> > @@ -92,4 +92,26 @@ test_expect_success 'git ls-files --format with --debug' '
> >         test_cmp expect actual
> >  '
> >
> > +test_expect_success 'git ls-files --format with skipworktree' '
>
> Should probably add a
>     test_when_finished "git sparse-checkout disable" &&
> at the beginning of this test, otherwise you are potentially causing
> confusion to future developers who try to add additional testcases to
> this file.
>

Agree.

> > +       mkdir dir1 dir2 &&
> > +       echo "file1" >dir1/file1.txt &&
> > +       echo "file2" >dir2/file2.txt &&
> > +       git add dir1 dir2 &&
> > +       git commit -m skipworktree &&
> > +       git sparse-checkout set dir1 &&
> > +       git ls-files --format="%(path) %(skipworktree)" >actual &&
> > +       cat >expect <<-\EOF &&
> > +       dir1/file1.txt false
> > +       dir2/file2.txt true
> > +       o1.txt false
> > +       o2.txt false
> > +       o3.txt false
> > +       o4.txt false
> > +       o5.txt false
> > +       o6.txt false
> > +       o7.txt false
> > +       EOF
> > +       test_cmp expect actual
> > +'
>
> To be honest, I don't yet see any compelling reason to use this new
> option.  Even if this patch is accepted, I'd just continue using "git
> ls-files -t" (both directly and in scripts) in preference to this.
> However, you have inspired me to try to fix up the ls-files
> documentation and remove the "semi-deprecated" label for the -t
> option.  Patches over here:
> https://github.com/gitgitgadget/git/pull/1463 ; I'll submit them in
> the next few days.

To be honest, right now I think %(skipworktree) just refines the
--format option's ability to read the index entry SKIP_WORKTREE
flag bits. It is probably still worth keeping.

Thanks,
ZheNing Hu