Re: [PATCH v2 05/10] split-index.c: dump "link" extension as json

>
> On Mon, Jun 24, 2019 at 08:02:21PM +0700, Nguyễn Thái Ngọc Duy wrote:
> > diff --git a/t/t3011-ls-files-json.sh b/t/t3011-ls-files-json.sh
> > index 082fe8e966..dbb572ce9d 100755
> > --- a/t/t3011-ls-files-json.sh
> > +++ b/t/t3011-ls-files-json.sh
> > @@ -44,4 +44,18 @@ test_expect_success 'ls-files --json, main entries, UNTR and TREE' '
> >       compare_json basic
> >  '
> >
> > +test_expect_success 'ls-files --json, split index' '
> > +     git init split &&
> > +     (
> > +             cd split &&
> > +             echo one >one &&
> > +             git add one &&
> > +             git update-index --split-index &&
> > +             echo updated >>one &&
> > +             test_must_fail git -c splitIndex.maxPercentChange=100 update-index --refresh &&
> > +             cp ../filter.sed . &&
> > +             compare_json split-index
> > +     )
> > +'
> > +
> >  test_done
> > diff --git a/t/t3011/split-index b/t/t3011/split-index
> > new file mode 100644
> > index 0000000000..cdcc4ddded
> > --- /dev/null
> > +++ b/t/t3011/split-index
> > @@ -0,0 +1,39 @@
> > +{
> > +  "version": 2,
> > +  "oid": <string>,
> > +  "mtime_sec": <number>,
> > +  "mtime_nsec": <number>,
> > +  "entries": [
> > +    {
> > +      "id": 0,
> > +      "name": "",
> > +      "mode": "100644",
> > +      "flags": 0,
> > +      "oid": <string>,
> > +      "stat": {
> > +        "ctime_sec": <number>,
> > +        "ctime_nsec": <number>,
> > +        "mtime_sec": <number>,
> > +        "mtime_nsec": <number>,
> > +        "device": <number>,
> > +        "inode": <number>,
> > +        "uid": <number>,
> > +        "gid": <number>,
> > +        "size": 4
> > +      },
> > +      "file_offset": <number>
> > +    }
> > +  ],
> > +  "extensions": {
> > +    "link": {
> > +      "file_offset": <number>,
> > +      "ext_size": <number>,
> > +      "oid": <string>,
> > +      "delete_bitmap": [
> > +      ],
> > +      "replace_bitmap": [
> > +        0
> > +      ]
> > +    }
> > +  }
> > +}
>
> This test is flaky, as reported in:
>
>   https://public-inbox.org/git/xmqqftno2mku.fsf@gitster-ct.c.googlers.com/
>
> This is because it relies on racy behaviour, namely that the following
> three commands
>
>     echo one >one &&
>     git add one &&
>     git update-index --split-index &&
>
> are executed within the same second, leaving 'one' racily clean.  To
> deal with the racily clean file, 5581a019ba (split-index: smudge and
> add racily clean cache entries to split index, 2018-10-11) kicks in,
> and 'one's smudged index entry is stored both in the shared index and
> in the split index.  That's why this test expects the offset 0 in the
> "replace_bitmap" array.
>
> However, it's possible that a second boundary is crossed between
> writing to 'one' and splitting the index, and then 'one' is not racily
> clean, and its index entry is only stored in the shared index.
> Consequently, there are no index entries in the split index, so the
> "replace_bitmap" array ends up being empty, ultimately failing the
> test.

> A 'test-tool chmtime' invocation or two could make the test
> deterministic (i.e it could make sure that 'one' is either always
> racily clean or it never is, whichever is preferred).
>
> What I still don't understand, however, is that when the test fails
> this way, then the "entries" array ends up being empty as well.  It
> looks as if the JSON dump included only index entries that were
> actually stored in '.git/index', but omitted entries that were only
> present in the shared index.  I think this is wrong, and it should
> dump the unified view of the split and shared indexes.  Or include all
> entries from the shared index as well.  Or perhaps I'm completely
> missing something...