On 11/12, Junio C Hamano wrote:
> Thomas Gummerer <t.gummerer@xxxxxxxxx> writes:
>
> >> > From what you are saying above, and from my testing I think this
> >> > refresh is actually unnecessary, and we could just remove it outright.
> >>
> >> Perhaps. But later it will bite us when somebody wants to rewrite
> >> the "status at the end" part in C.
> >
> > Hmm, wouldn't the not re-reading the index part bite us there, rather
> > than the not refreshing the index?
>
> Yes. Just removing the refresh-and-write that caused us to write
> out incorrect data would "fix" the bug, while leaving the bug of not
> re-reading to bite us later.
>
> > Below is the patch that I believe has the least chances of biting us
> > in the future, with the appropriate updated tests. I had considered
> > leaving the 'refresh_and_write_cache()' call there, but as I was
> > writing the commit message I had a harder and harder time justifying
> > that, so it's gone now, which I think is the right thing to do.
> > Leaving it there would be okay as well, however I don't think it would
> > have any benefit.
> >
> > --- >8 ---
> > Subject: [PATCH] stash: make sure we have a valid index before writing it
> >
> > In 'do_apply_stash()' we refresh the index in the end. Since
> > 34933d0eff ("stash: make sure to write refreshed cache", 2019-09-11),
> > we also write that refreshed index when --quiet is given to 'git stash
> > apply'.
> >
> > However if '--index' is not given to 'git stash apply', we also
> > discard the index in the else clause just before. This leads to
> > writing the discarded index, which means we essentially write an empty
> > index file. This is obviously not correct, or the behaviour the user
> > wanted. We should not modify the users index without being asked to
> > do so.
> >
> > Make sure to re-read the index after discarding the current in-core
> > index, to avoid dealing with outdated information.
>
> Yup. The "!has_index" codepath calls update_index() that turns the
> on-disk index into the desired shape (would it help explaining that
> in the previous paragraph, by the way?) so all we need to do is to
> read it back into core. Makes sense.
Will add some more explanation about that.
> > We could also drop the 'discard_cache()' + 'read_cache()', however
> > that would make it easy to fall into the same trap as 34933d0eff did,
> > so it's better to avoid that.
>
> This is the discarded alternative of the main fix we saw earlier.
> Perhaps it may make the flow of thought easier to follow if we moved
> it up before talking about "refresh-and-write can be thrown away"?
Thanks, will move.
> > Signed-off-by: Thomas Gummerer <t.gummerer@xxxxxxxxx>
> > ---
> > builtin/stash.c | 6 ++----
> > t/t3903-stash.sh | 5 ++++-
> > 2 files changed, 6 insertions(+), 5 deletions(-)
> >
> > diff --git a/builtin/stash.c b/builtin/stash.c
> > index ab30d1e920..d00567285f 100644
> > --- a/builtin/stash.c
> > +++ b/builtin/stash.c
> > @@ -482,12 +482,10 @@ static int do_apply_stash(const char *prefix, struct stash_info *info,
> > return -1;
> >
> > discard_cache();
> > + read_cache();
>
> A comment
>
> /* read back the result of update_index() back from the disk */
>
> before discard_cache() may be warranted?
Yeah that makes sense, will add.
> > }
> >
> > - if (quiet) {
> > - if (refresh_and_write_cache(REFRESH_QUIET, 0, 0))
> > - warning("could not refresh index");
> > - } else {
>
> OK.
>
> > + if (!quiet) {
> > struct child_process cp = CHILD_PROCESS_INIT;
> >
> > /*
> > diff --git a/t/t3903-stash.sh b/t/t3903-stash.sh
> > index 392954d6dd..b1c973e3d9 100755
> > --- a/t/t3903-stash.sh
> > +++ b/t/t3903-stash.sh
> > @@ -232,8 +232,9 @@ test_expect_success 'save -q is quiet' '
> > test_must_be_empty output.out
> > '
> >
> > -test_expect_success 'pop -q is quiet' '
> > +test_expect_success 'pop -q works and is quiet' '
> > git stash pop -q >output.out 2>&1 &&
> > + test bar = "$(git show :file)" &&
>
> Ah, this is to ensure that we didn't lose the "file" from the index?
>
> Denton is on the quest of removing "$(git command substitution)"
> used in a way that might hide the error from git invocation in a
> separate thread [*1*]. This may want to become
>
> git rev-parse --verify :file &&
>
> or
>
> git show :file >actual && echo bar >expect &&
> test_cmp expect actual &&
>
> perhaps?
Hmm I just copy-pasted this from somewhere else in this test file.
I'll add a preparatory patch getting rid of "$(git command substitution)"
as I don't believe Denton got to t3903 yet.
There's some more opportunities for modernization of this test file,
but I refrained from doing that to not blow up this bug fix series too
much.
> > test_must_be_empty output.out
> > '
> >
> > @@ -242,6 +243,8 @@ test_expect_success 'pop -q --index works and is quiet' '
> > git add file &&
> > git stash save --quiet &&
> > git stash pop -q --index >output.out 2>&1 &&
> > + git diff-files file2 >file2.diff &&
> > + test_must_be_empty file2.diff &&
> > test foo = "$(git show :file)" &&
> > test_must_be_empty output.out
> > '
>
> Dittto.
>
> Thanks.
>
>
> [Reference]
>
> *1* <2f9052fd94ebb6fe93ea6fe2e7cd3c717635c822.1573517561.git.liu.denton@xxxxxxxxx>
>
> Note that "var=$(git subcmd)" is special and will signal us a failure
> of the git invocation.
