On Wed, Nov 16, 2022 at 2:04 AM ZheNing Hu <adlternative@xxxxxxxxx> wrote:
> Elijah Newren <newren@xxxxxxxxx> 于2022年11月16日周三 13:49写道：
> > On Mon, Nov 14, 2022 at 8:03 PM ZheNing Hu <adlternative@xxxxxxxxx> wrote:
> > > Elijah Newren via GitGitGadget <gitgitgadget@xxxxxxxxx> 于2022年11月6日周日 14:04写道：
[...]
> > The fact that files have been "vivified" is slightly ambiguous and
> > thus a bad way to define this set. When git vivifies files, it'll
> > clear the SKIP_WORKTREE bit. If an editor, or script external to git,
> > or something else restores the file, it will likely overlook that
> > detail. We want vivified files to be part of the sparse specification
> > when interacting with the working tree regardless of whether the
> > SKIP_WORKTREE bit was correctly updated, so I defined it the way I did
> > to remove such ambiguity. (I guess I should note that as per
> > af6a51875a ("repo_read_index: clear SKIP_WORKTREE bit from files
> > present in worktree", 2022-01-14), git will clear the SKIP_WORKTREE
> > bit for files present in the working copy as one of the first things
> > it does, but that could leave people wondering whether I meant the
> > SKIP_WORKTREE bit was set as of the time of git invocation. So, I
> > explicitly call out files present in the working copy for which the
> > index entry has the SKIP_WORKTREE bit set, so folks know these files
> > are definitely included in the sparse specification.)
> >
>
> You are right: the definition of vivifying explicitly clears the
> SKIP_WORKTREE bit from the index, So the behavior described
> here is not vivifying, but very much like vivifying: clear the
> SKIP_WORKTREE bit from index_entry in memory instead of actually
> clearing it from the index on disk.
No, the definition of vivifying in my PR does not explicitly state
that; in fact, it doesn't even imply that it always happens. The
wording was:
+vivifying: When a command restores a tracked file to the working tree (and
+ hopefully also clears the SKIP_WORKTREE bit in the index for that
+ file), this is referred to as "vivifying" the file.
In particular, it's important to note that:
* some git commands won't even clear the SKIP_WORKTREE bit when they
vivify files (e.g. I think git-checkout-index falls in this category,
for example); we could never audit all codepaths and fix them all.
But when they restore files we still consider that to be "vivifying"
those paths whether or not they clear the SKIP_WORKTREE bit.
* I considered the restoration of files by non-git commands (e.g.
"echo contents >filename") to also be considered "vivifying" of those
files, and I certainly don't expect non-git commands to clear the
SKIP_WORKTREE bit.
> Anyway, for the file on "worktree", we can use ce_skip_worktree(ce)
> to check if it belongs to the sparse specification.
Yes, due to the commit af6a51875a referenced above, our implementation
can just check this. Except, it's !ce_skep_worktree(ce), of course.
:-)
> > > I think we can add some examples to describe these terms.
> > >
> > > #!/bin/sh
> > >
> > > set -x
> > >
> > > rm -rf mono-repo
> > > git init mono-repo -b main
> > > (
> > > cd mono-repo &&
> > > mkdir p1 p2 &&
> > > echo a >p1/a &&
> > > echo b >p1/b &&
> > > echo a >p2/a &&
> > > echo b >p2/b &&
> > > git add . &&
> > > git commit -m ok &&
> > > git sparse-checkout set p1 &&
> > > git ls-files -t &&
> > > echo a >>p1/a &&
> > > echo b >>p1/b &&
> > > mkdir p2 p3 &&
> > > echo next >>p2/a &&
> > > echo next >>p3/c &&
> > > git add p3/c &&
>
> Here I forget a "--sparse"
>
> > > # p2/a and p3/c vivify
> > > git ls-files -t &&
> > > # compare wortree/commit
> > > git --no-pager diff HEAD --name-only
> > > )
> >
> > You've added a bunch of code with this example, but you have not said
> > what the output should be, so how exactly does this help describe the
> > terms?
> >
>
> We create a repo with two sub projects p1/ p2/, then set
> sparsity directory p1.
>
> First git ls-files -t outputs:
>
> H p1/a
> H p1/b
> S p2/a
> S p2/b
>
> It shows that index entries in p2 are skip-worktree.
> Then we restore p2/a in the working tree and create a
> new file p3/c and add it to the index.
>
> The second git ls-files -t output:
>
> H p1/a
> H p1/b
> H p2/a
> S p2/b
> H p3/c
>
> p2/a and p3/c are not in sparse patterns, but they are in
> sparse specification. It's like a special "vivifying".
What do you mean by a "special" vivifying?
Also, there's multiple problems with using your example so far to
describe the sparse specification:
* You are specifying `git ls-files -t` output here, which may or may
not ignore the sparse specification (as mentioned elsewhere in the new
document); if it doesn't, then specifying how commands behave when
they ignore the sparse specification as a way of describing the sparse
specification seems less than helpful. We could overlook that, but:
* You didn't specify the output for `git diff HEAD` and `git diff
REV` was one of the cases where the sparse specification matters.
Explaining how `git diff REV` works relative to the sparse
specification seems like the point of you having an example, BUT even
if you tried to do that with this particular example:
1) Users are probably left wondering whether p3/c is present in the
working copy at the time these commands run, and thus whether it is in
the sparse specification for that reason rather than for the reason of
there being a difference in the index relative to HEAD.
2) You didn't specify the differences in the output between behavior
A and behavior B for your example, if any, which might be needed for
an appropriate contrast. Further...
3) You picked an example where the output might be the same for both
behavior A and behavior B, and since behavior B ignores the sparse
specification, it's really hard to see how this example helps
elucidate the meaning of the sparse specification.
So, I'm still not seeing how this example helps describe the sparse
specification.
> > > > + * When modifying or showing results from the index, the sparse
> > > > + specification is the set of files with a clear SKIP_WORKTREE bit
> > > > + or that differ in the index from HEAD.
> > >
> > > #!/bin/sh
> > >
> > > set -x
> > >
> > > rm -rf mono-repo
> > > git init mono-repo -b main
> > > (
> > > cd mono-repo &&
> > > mkdir p1 p2 &&
> > > echo a >p1/a &&
> > > echo b >p1/b &&
> > > echo a >p2/a &&
> > > echo b >p2/b &&
> > > git add . &&
> > > git commit -m ok &&
> > > git sparse-checkout set p1 &&
> > > git update-index --chmod=+x p2/a &&
> > > # compare commit/index
> > > git --no-pager diff --cached --name-only
> > > )
> >
> > Same issue here; you haven't stated the expected output of these
> > commands, so I don't see how they help with the description at all.
> >
>
> Here only output p2/a:
>
> p2/a is out of sparse patterns, but this index entry mode has been
> changed compared to HEAD. So we should consider it as a part of
> sparse specification.
Same thing here about the fact that you've given an example with the
same output under behavior A and behavior B, and since behavior B
ignores the sparse specification, I'm not sure your example elucidates
the sparse specification that much other than to make clear it
includes more than the sparse patterns. But didn't my wording already
do that?
(Note that `git diff --cached` without a revision is just inherently
susceptible to this problem; it should always produce the same output
under both modes.)
> > Perhaps it's worth noting why I think the sparse specification should
> > be extended when dealing with the index:
> >
> > * "mergy" commands (merge, rebase, cherry-pick, am, revert) can
> > modify the index outside the sparsity patterns, without creating a
> > commit.
> > * `git commit` (or `rebase --continue`, or whatever) will create a
> > commit from whatever staged versions of files there are
> > => `git status` should show what is about to be committed
> > => `git diff --cached --name-only` ought to be usable to show what
> > is to be committed
> > => `git grep --cached ...` ought to be usable to search through what
> > is about to be committed
> >
> > See also https://lore.kernel.org/git/CABPp-BESkb=04vVnqTvZyeCa+7cymX7rosUW3rhtA02khMJKHA@xxxxxxxxxxxxxx/
> > (starting with the paragraph with "leery" in it), and the thread
> > starting there. If the sparse specification is not expanded, users
> > will get some nasty surprises, and the only other alternative I can
> > think of to avoid such surprises would be making several commands
> > always run full tree. Running full-tree with a non-default option to
> > run sparse forces behavior A folks into a "pick your poison"
> > situation, which is not nice. Extending the sparse specification to
> > include files whose index entries do not match HEAD for index-related
> > operations provides the nice middle ground that avoids such usability
> > problems while also allowing users to avoid operating on a full tree.
> >
>
> I can understand the reason why we need to extend sparse specification:
> index often needs to handle files that are not in the sparse pattern.
Yep!
[...]
> > > A** : Some users are _only_ interested in the sparse portion of the repo,
> > > but they want to download all the blobs in it to avoid some unnecessary
> > > network connections afterwards.
> >
> > Here you just repeated `A*` but relabelled it as `A**`. Yes, this one
> > is explicitly tied to partial clone behavior.
>
> Ah, `A*` part say “so things like `git log -S${SEARCH_TERM} -p`
> or `git grep ${SEARCH_TERM} OLDREV ` would need to be prepared to provide
> partial results that depend on what happens to have been downloaded."
>
> So I think it's probably a lot like the behavior after a shallow
> clone: git log -p or other
> git commands returning partial results.
Yes, though not being a fan of shallow clones, the comparison makes me
recoil slightly. ;-)
> The expectation of A** is to have all blobs under the entire sparse-patterns.
Ah, I misread your `A**`. I agree there are users that want to do
this; I'm one of them.
But how does that affect the results that users see from running
operations? Does it change any definitions or categorize any commands
differently, or affect anything in the document? Why is it worth
calling out that people want full history of the paths matching the
sparsity patterns?
> >
> > [...]
> > > > + 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 just might have caused this in one particular case. So it's not very
> important at the moment. But it's worth noting that many shells, IDEs’
> git plugins
> may also need to understand sparse-checkout properly, otherwise it can
> cause some usability problems.
Why do these tools need to understand sparse-checkout? What kind of
usability problems could occur? Can you describe what range of issues
can occur, or even give any specific examples?
The whole point of the document is trying to address remaining
sparse-checkout issues, and we even have a section highlighting known
current problems. If you know of additional issues, it would be great
to make them known, but I cannot figure out what you might be referring
to from these vague descriptions.
