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serialize-status: serialize global and repo-local exclude file metadata #1

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jeffhostetler
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@jeffhostetler jeffhostetler commented Jul 23, 2018

Changes to the global or repo-local excludes files can change the
results returned by "git status" for untracked files. Therefore,
it is important that the exclude-file values used during serialization
are still current at the time of deserialization.

Teach "git status --serialize" to report metadata on the user's global
exclude file (which defaults to "$XDG_HOME/git/ignore") and for the
repo-local excludes file (which is in ".git/info/excludes"). Serialize
will record the pathnames and mtimes for these files in the serialization
header (next to the mtime data for the .git/index file).

Teach "git status --deserialize" to validate this new metadata. If either
exclude file has changed since the serialization-cache-file was written,
then deserialize will reject the cache file and force a full/normal status
run.

Signed-off-by: Jeff Hostetler jeffhost@microsoft.com

/*
* In dir.c:setup_standard_excludes() they use either the value of
* the "core.excludefile" variable (stored in the global "excludes_file"
* variable) -or- the default value "$XDG_HOME/git/ignore". This is done
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From the documentation for core.excludesfile, it looks like we might also need to consider $HOME/.config/git/ignore as well?

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the xdg_config_home() routine that i'm calling takes care of all of that.

strbuf_addf(sb, "%s E (not-found) %s", key, path);
else
strbuf_addf(sb, "%s E (other) %s", key, path);
}
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style: } else {? (instead of putting else { on its own line?

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yeah, i think i've seen both ways in the code. i'll check if there's a preferred way.

/*
* WARNING: there are also per-directory .gitignore files that can change
* the results reported by status. If you run a serialize with untracked
* .gitignore files and then change a per-directory .gitignore file or
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I was confused when I initially read this, but I think I understand it now. untracked .gitignore files - I think this is referring to untracked files that match an exclude pattern, rather than .gitignore files that are untracked.

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I probably made the comment more confusing that it needs to be.

Every directory is allowed to have a .gitignore file. Their presence can alter the output of status.
If a new .gitignore file is created (after a status snapshot is created) -or- if an existing .gitignore
file is modified (after the snapshot is created), the results of status may change.

The first type I called untracked. The second type I called unstaged. The main point is that the
set of what should be excluded/ignored has changed and the index was not updated. If either
type of .gitignore files are added/staged, the index will be updated and its mtime changed, so
the existing checks will consider the status cache invalid. My point was that those 2 types of
.gitignore files can exist and the index mtime won't have changed.

free(path);
}

/*
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@jeffhostetler jeffhostetler Jul 26, 2018

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@jamill Does the following comment block better explain what we were talking about?

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👍

* [] This includes changes to tracked files.
* [] This includes changes to tracked .gitignore files that might change
* untracked file reporting.
* [] This includes the creation of new, untracked per-directory .gitnore
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@jamill jamill Jul 26, 2018

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sp: git[ig]nore

Changes to the global or repo-local excludes files can change the
results returned by "git status" for untracked files.  Therefore,
it is important that the exclude-file values used during serialization
are still current at the time of deserialization.

Teach "git status --serialize" to report metadata on the user's global
exclude file (which defaults to "$XDG_HOME/git/ignore") and for the
repo-local excludes file (which is in ".git/info/excludes").  Serialize
will record the pathnames and mtimes for these files in the serialization
header (next to the mtime data for the .git/index file).

Teach "git status --deserialize" to validate this new metadata.  If either
exclude file has changed since the serialization-cache-file was written,
then deserialize will reject the cache file and force a full/normal status
run.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
@jeffhostetler jeffhostetler merged commit 54396ce into microsoft:gvfs-2.18.0 Jul 27, 2018
kewillford pushed a commit to kewillford/git that referenced this pull request Sep 4, 2018
When "git rebase -i" is told to squash two or more commits into
one, it labeled the log message for each commit with its number.
It correctly called the first one "1st commit", but the next one
was "commit microsoft#1", which was off-by-one.  This has been corrected.

* pw/rebase-i-squash-number-fix:
  rebase -i: fix numbering in squash message
kewillford pushed a commit to kewillford/git that referenced this pull request Sep 4, 2018
The verbose output of the test 'reword without issues functions as
intended' in 't3423-rebase-reword.sh', added in a9279c6 (sequencer:
do not squash 'reword' commits when we hit conflicts, 2018-06-19),
contains the following error output:

  sed: -e expression microsoft#1, char 2: extra characters after command

This error comes from within the 'fake-editor.sh' script created by
'lib-rebase.sh's set_fake_editor() function, and the root cause is the
FAKE_LINES="pick 1 reword 2" variable in the test in question, in
particular the "pick" word.  'fake-editor.sh' assumes 'pick' to be the
default rebase command and doesn't support an explicit 'pick' command
in FAKE_LINES.  As a result, 'pick' will be used instead of a line
number when assembling the following 'sed' script:

  sed -n picks/^pick/pick/p

which triggers the aforementioned error.

Luckily, this didn't affect the test's correctness: the erroring 'sed'
command doesn't write anything to the todo script, and processing the
rest of FAKE_LINES generates the desired todo script, as if that
'pick' command were not there at all.

The minimal fix would be to remove the 'pick' word from FAKE_LINES,
but that would leave us susceptible to similar issues in the future.

Instead, teach the fake-editor script to recognize an explicit 'pick'
command, which is still a fairly trivial change.

In the future we might want to consider reinforcing this fake editor
script with an &&-chain and stricter parsing of the FAKE_LINES
variable (e.g. to error out when encountering unknown rebase commands
or commands and line numbers in the wrong order).

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
kewillford pushed a commit to kewillford/git that referenced this pull request Sep 4, 2018
serialize-status: serialize global and repo-local exclude file metadata
kewillford pushed a commit that referenced this pull request Sep 17, 2018
serialize-status: serialize global and repo-local exclude file metadata
dscho pushed a commit that referenced this pull request Oct 15, 2018
serialize-status: serialize global and repo-local exclude file metadata
dscho pushed a commit that referenced this pull request Oct 18, 2018
serialize-status: serialize global and repo-local exclude file metadata
dscho pushed a commit that referenced this pull request Nov 21, 2018
Change "fetch" to treat "+" in refspecs (aka --force) to mean we
should clobber a local tag of the same name.

This changes the long-standing behavior of "fetch" added in
853a369 ("[PATCH] Multi-head fetch.", 2005-08-20). Before this
change, all tag fetches effectively had --force enabled. See the
git-fetch-script code in fast_forward_local() with the comment:

    > Tags need not be pointing at commits so there is no way to
    > guarantee "fast-forward" anyway.

That commit and the rest of the history of "fetch" shows that the
"+" (--force) part of refpecs was only conceived for branch updates,
while tags have accepted any changes from upstream unconditionally and
clobbered the local tag object. Changing this behavior has been
discussed as early as 2011[1].

The current behavior doesn't make sense to me, it easily results in
local tags accidentally being clobbered. We could namespace our tags
per-remote and not locally populate refs/tags/*, but as with my
97716d2 ("fetch: add a --prune-tags option and fetch.pruneTags
config", 2018-02-09) it's easier to work around the current
implementation than to fix the root cause.

So this change implements suggestion #1 from Jeff's 2011 E-Mail[1],
"fetch" now only clobbers the tag if either "+" is provided as part of
the refspec, or if "--force" is provided on the command-line.

This also makes it nicely symmetrical with how "tag" itself works when
creating tags. I.e. we refuse to clobber any existing tags unless
"--force" is supplied. Now we can refuse all such clobbering, whether
it would happen by clobbering a local tag with "tag", or by fetching
it from the remote with "fetch".

Ref updates outside refs/{tags,heads/* are still still not symmetrical
with how "git push" works, as discussed in the recently changed
pull-fetch-param.txt documentation. This change brings the two
divergent behaviors more into line with one another. I don't think
there's any reason "fetch" couldn't fully converge with the behavior
used by "push", but that's a topic for another change.

One of the tests added in 31b808a ("clone --single: limit the fetch
refspec to fetched branch", 2012-09-20) is being changed to use
--force where a clone would clobber a tag. This changes nothing about
the existing behavior of the test.

1. https://public-inbox.org/git/20111123221658.GA22313@sigill.intra.peff.net/

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
dscho pushed a commit that referenced this pull request Nov 21, 2018
check_one_conflict() compares `i` to `active_nr` in two places to avoid
buffer overruns, but left out an important third location.

The code did used to have a check here comparing i to active_nr, back
before commit fb70a06 ("rerere: fix an off-by-one non-bug",
2015-06-28), however the code at the time used an 'if' rather than a
'while' meaning back then that this loop could not have read past the
end of the array, making the check unnecessary and it was removed.
Unfortunately, in commit 5eda906 ("rerere: handle conflicts with
multiple stage #1 entries", 2015-07-24), the 'if' was changed to a
'while' and the check comparing i and active_nr was not re-instated,
leading to this problem.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
dscho pushed a commit that referenced this pull request Nov 21, 2018
Reimplement oidset using khash.h in order to reduce its memory footprint
and make it faster.

Performance of a command that mainly checks for duplicate objects using
an oidset, with master and Clang 6.0.1:

  $ cmd="./git-cat-file --batch-all-objects --unordered --buffer --batch-check='%(objectname)'"

  $ /usr/bin/time $cmd >/dev/null
  0.22user 0.03system 0:00.25elapsed 99%CPU (0avgtext+0avgdata 48484maxresident)k
  0inputs+0outputs (0major+11204minor)pagefaults 0swaps

  $ hyperfine "$cmd"
  Benchmark #1: ./git-cat-file --batch-all-objects --unordered --buffer --batch-check='%(objectname)'

    Time (mean ± σ):     250.0 ms ±   6.0 ms    [User: 225.9 ms, System: 23.6 ms]

    Range (min … max):   242.0 ms … 261.1 ms

And with this patch:

  $ /usr/bin/time $cmd >/dev/null
  0.14user 0.00system 0:00.15elapsed 100%CPU (0avgtext+0avgdata 41396maxresident)k
  0inputs+0outputs (0major+8318minor)pagefaults 0swaps

  $ hyperfine "$cmd"
  Benchmark #1: ./git-cat-file --batch-all-objects --unordered --buffer --batch-check='%(objectname)'

    Time (mean ± σ):     151.9 ms ±   4.9 ms    [User: 130.5 ms, System: 21.2 ms]

    Range (min … max):   148.2 ms … 170.4 ms

Initial-patch-by: Jeff King <peff@peff.net>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
dscho pushed a commit that referenced this pull request Nov 21, 2018
Ever since the split index feature was introduced [1], refreshing a
split index is prone to a variant of the classic racy git problem.
There are a couple of unrelated tests in the test suite that
occasionally fail when run with 'GIT_TEST_SPLIT_INDEX=yes', but
't1700-split-index.sh', the only test script focusing solely on split
index, has never noticed this issue, because it only cares about how
the index is split under various circumstances and all the different
ways to turn the split index feature on and off.

Add a dedicated test script 't1701-racy-split-index.sh' to exercise
the split index feature in racy situations as well; kind of a
"t0010-racy-git.sh for split index" but with modern style (the tests
do everything in &&-chained list of commands in 'test_expect_...'
blocks, and use 'test_cmp' for more informative output on failure).

The tests cover the following sequences of index splitting, updating,
and racy file modifications, with the last two cases demonstrating the
racy split index problem:

  1. Split the index while adding a racily clean file:

       echo "cached content" >file
       git update-index --split-index --add file
       echo "dirty worktree" >file    # size stays the same

     This case already works properly.  Even though the cache entry's
     stat data matches with the modifid file in the worktree,
     subsequent git commands will notice that the (split) index and
     the file have the same mtime, and then will go on to check the
     file's content and notice its dirtiness.

  2. Add a racily clean file to an already split index:

       git update-index --split-index
       echo "cached content" >file
       git update-index --add file
       echo "dirty worktree" >file

     This case already works properly.  After the second 'git
     update-index' writes the newly added file's cache entry to the
     new split index, it basically works in the same way as case #1.

  3. Split the index when it (i.e. the not yet splitted index)
     contains a racily clean cache entry, i.e. an entry whose cached
     stat data matches with the corresponding file in the worktree and
     the cached mtime matches that of the index:

       echo "cached content" >file
       git update-index --add file
       echo "dirty worktree" >file
       # ... wait ...
       git update-index --split-index --add other-file

     This case already works properly.  The shared index is written by
     do_write_index(), i.e. the same function that is responsible for
     writing "regular" and split indexes as well.  This function
     cleverly notices the racily clean cache entry, and writes the
     entry to the new shared index with smudged stat data, i.e. file
     size set to 0.  When subsequent git commands read the index, they
     will notice that the smudged stat data doesn't match with the
     file in the worktree, and then go on to check the file's content
     and notice its dirtiness.

  4. Update the split index when it contains a racily clean cache
     entry:

       git update-index --split-index
       echo "cached content" >file
       git update-index --add file
       echo "dirty worktree" >file
       # ... wait ...
       git update-index --add other-file

     This case already works properly.  After the second 'git
     update-index' the newly added file's cache entry is only stored
     in the split index.  If a cache entry is present in the split
     index (even if it is a replacement of an outdated entry in the
     shared index), then it will always be included in the new split
     index on subsequent split index updates (until the file is
     removed or a new shared index is written), independently from
     whether the entry is racily clean or not.  When do_write_index()
     writes the new split index, it notices the racily clean cache
     entry, and smudges its stat date.  Subsequent git commands
     reading the index will notice the smudged stat data and then go
     on to check the file's content and notice its dirtiness.

  5. Update the split index when a racily clean cache entry is stored
     only in the shared index:

       echo "cached content" >file
       git update-index --split-index --add file
       echo "dirty worktree" >file
       # ... wait ...
       git update-index --add other-file

     This case fails due to the racy split index problem.  In the
     second 'git update-index' prepare_to_write_split_index() decides,
     among other things, which cache entries stored only in the shared
     index should be replaced in the new split index.  Alas, this
     function never looks out for racily clean cache entries, and
     since the file's stat data in the worktree hasn't changed since
     the shared index was written, the entry won't be replaced in the
     new split index.  Consequently, do_write_index() doesn't even get
     this racily clean cache entry, and can't smudge its stat data.
     Subsequent git commands will then see that the index has more
     recent mtime than the file and that the (not smudged) cached stat
     data still matches with the file in the worktree, and,
     ultimately, will erroneously consider the file clean.

  6. Update the split index after unpack_trees() copied a racily clean
     cache entry from the shared index:

       echo "cached content" >file
       git update-index --split-index --add file
       echo "dirty worktree" >file
       # ... wait ...
       git read-tree -m HEAD

     This case fails due to the racy split index problem.  This
     basically fails for the same reason as case #5 above, but there
     is one important difference, which warrants the dedicated test.
     While that second 'git update-index' in case #5 updates
     index_state in place, in this case 'git read-tree -m' calls
     unpack_trees(), which throws out the entire index, and constructs
     a new one from the (potentially updated) copies of the original's
     cache entries.  Consequently, when prepare_to_write_split_index()
     gets to work on this reconstructed index, it takes a different
     code path than in case #5 when deciding which cache entries in
     the shared index should be replaced.  The result is the same,
     though: the racily clean cache entry goes unnoticed, it isn't
     added to the split index with smudged stat data, and subsequent
     git commands will then erroneously consider the file clean.

Note that in the last two 'test_expect_failure' cases I omitted the
'#' (as in nr. of trial) from the tests' description on purpose for
now, as it breakes the TAP output [2]; it will be added at the end of
the series, when those two tests will be flipped to
'test_expect_success'.

[1] In the branch leading to the merge commit v2.1.0-rc0~45 (Merge
    branch 'nd/split-index', 2014-07-16).

[2] In the TAP output a '#' should separate the test's description
    from the TODO directive emitted by 'test_expect_failure'.  The
    additional '#' in "#$trial" interferes with this, the test harness
    won't recognize the TODO directive, and will report that those
    tests failed unexpectedly.

Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
dscho pushed a commit that referenced this pull request Nov 21, 2018
serialize-status: serialize global and repo-local exclude file metadata
dscho pushed a commit that referenced this pull request Nov 26, 2018
serialize-status: serialize global and repo-local exclude file metadata
dscho added a commit that referenced this pull request Nov 3, 2023
Includes these pull requests:

	#1
	#6
	#10
	#11
	#157
	#212
	#260
	#270

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
dscho pushed a commit that referenced this pull request Nov 3, 2023
When "update-index --unresolve $path" cannot find the resolve-undo
record for the path the user requested to unresolve, it stuffs the
blobs from HEAD and MERGE_HEAD to stage #2 and stage #3 as a
fallback.  For this reason, the operation does not even start unless
both "HEAD" and "MERGE_HEAD" exist.

This is suboptimal in a few ways:

 * It does not recreate stage #1.  Even though it is a correct
   design decision not to do so (because it is impossible to
   recreate in general cases, without knowing how we got there,
   including what merge strategy was used), it is much less useful
   not to have that information in the index.

 * It limits the "unresolve" operation only during a conflicted "git
   merge" and nothing else.  Other operations like "rebase",
   "cherry-pick", and "switch -m" may result in conflicts, and the
   user may want to unresolve the conflict that they incorrectly
   resolved in order to redo the resolution, but the fallback would
   not kick in.

 * Most importantly, the entire "unresolve" operation is disabled
   after a conflicted merge is committed and MERGE_HEAD is removed,
   even though the index has perfectly usable resolve-undo records.

By lazily reading the HEAD and MERGE_HEAD only when we need to go to
the fallback codepath, we will allow cases where resolve-undo
records are available (which is 100% of the time, unless the user is
reading from an index file created by Git more than 10 years ago) to
proceed even after a conflicted merge was committed, during other
mergy operations that do not use MERGE_HEAD, or after the result of
such mergy operations has been committed.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
dscho pushed a commit that referenced this pull request Nov 3, 2023
When t5583-push-branches.sh was originally introduced via 425b4d7
(push: introduce '--branches' option, 2023-05-06), it was not leak-free.
In fact, the test did not even run correctly until 022fbb6 (t5583:
fix shebang line, 2023-05-12), but after applying that patch, we see a
failure at t5583.8:

    ==2529087==ERROR: LeakSanitizer: detected memory leaks

    Direct leak of 384 byte(s) in 1 object(s) allocated from:
        #0 0x7fb536330986 in __interceptor_realloc ../../../../src/libsanitizer/lsan/lsan_interceptors.cpp:98
        #1 0x55e07606cbf9 in xrealloc wrapper.c:140
        #2 0x55e075fb6cb3 in prio_queue_put prio-queue.c:42
        #3 0x55e075ec81cb in get_reachable_subset commit-reach.c:917
        #4 0x55e075fe9cce in add_missing_tags remote.c:1518
        #5 0x55e075fea1e4 in match_push_refs remote.c:1665
        #6 0x55e076050a8e in transport_push transport.c:1378
        #7 0x55e075e2eb74 in push_with_options builtin/push.c:401
        #8 0x55e075e2edb0 in do_push builtin/push.c:458
        #9 0x55e075e2ff7a in cmd_push builtin/push.c:702
        #10 0x55e075d8aaf0 in run_builtin git.c:452
        #11 0x55e075d8af08 in handle_builtin git.c:706
        #12 0x55e075d8b12c in run_argv git.c:770
        #13 0x55e075d8b6a0 in cmd_main git.c:905
        #14 0x55e075e81f07 in main common-main.c:60
        #15 0x7fb5360ab6c9 in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58
        #16 0x7fb5360ab784 in __libc_start_main_impl ../csu/libc-start.c:360
        #17 0x55e075d88f40 in _start (git+0x1ff40) (BuildId: 38ad998b85a535e786129979443630d025ec2453)

    SUMMARY: LeakSanitizer: 384 byte(s) leaked in 1 allocation(s).

This leak was addressed independently via 68b5117 (commit-reach: fix
memory leak in get_reachable_subset(), 2023-06-03), which makes t5583
leak-free.

But t5583 was not in the tree when 68b5117 was written, and the two
only met after the latter was merged back in via 693bde4 (Merge
branch 'mh/commit-reach-get-reachable-plug-leak', 2023-06-20).

At that point, t5583 was leak-free. Let's mark it as such accordingly.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
dscho added a commit that referenced this pull request Nov 3, 2023
Includes these pull requests:

	#1
	#6
	#10
	#11
	#157
	#212
	#260
	#270

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
dscho added a commit that referenced this pull request Nov 3, 2023
Includes these pull requests:

	#1
	#6
	#10
	#11
	#157
	#212
	#260
	#270

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
dscho added a commit that referenced this pull request Nov 5, 2023
The `linux-leaks` job has become a lot more aggressive, failing the
following test cases:

- t0001.52 extensions.objectFormat is not allowed with repo version 0
- t1302.3 gitdir selection on unsupported repo
- t1302.4 gitdir not required mode
- t1302.5 gitdir required mode
- t1302.9 abort version=1 no-such-extension
- t1302.12 abort version=0 noop-v1

The reason is that the `commondir` strbuf _is_ sometimes initialized
_even if_ `discover_git_directory()` fails. The symptom:

    Direct leak of 24 byte(s) in 1 object(s) allocated from:
        #0 0x7f2e80ed8293 in __interceptor_realloc ../../../../src/libsanitizer/lsan/lsan_interceptors.cpp:98
        #1 0x5603ff6ae674 in xrealloc wrapper.c:138
        #2 0x5603ff661801 in strbuf_grow strbuf.c:101
        #3 0x5603ff662417 in strbuf_add strbuf.c:300
        #4 0x5603ff653e2b in strbuf_addstr strbuf.h:310
        #5 0x5603ff65703b in setup_git_directory_gently_1 setup.c:1329
        #6 0x5603ff65731b in discover_git_directory_reason setup.c:1388
        #7 0x5603ff55b6c0 in discover_git_directory setup.h:79
        #8 0x5603ff55b7ce in hook_path_early hook.c:35
        #9 0x5603ff55b97d in find_hook hook.c:77
        #10 0x5603ff55bcd3 in run_hooks_opt hook.c:189
        #11 0x5603ff37ca05 in run_pre_command_hook git.c:457
        #12 0x5603ff37ce0a in run_builtin git.c:532
        #13 0x5603ff37d37e in handle_builtin git.c:798
        #14 0x5603ff37d65a in run_argv git.c:867
        #15 0x5603ff37dc8e in cmd_main git.c:1007
        #16 0x5603ff48f4ee in main common-main.c:62
        #17 0x7f2e80cabd8f in __libc_start_call_main ../sysdeps/nptl/libc_start_call_main.h:58

The fix is easy: always release the `strbuf`s, even when the discovery
of the Git directory failed.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
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dscho added a commit that referenced this pull request Oct 9, 2024
An internal customer reported a segfault when running `git
sparse-checkout set` with the `index.sparse` config enabled. I was
unable to reproduce it locally, but with their help we debugged into the
failing process and discovered the following stacktrace:

```
#0  0x00007ff6318fb7b0 in rehash (map=0x3dfb00d0440, newsize=1048576) at hashmap.c:125
#1  0x00007ff6318fbc66 in hashmap_add (map=0x3dfb00d0440, entry=0x3dfb5c58bc8) at hashmap.c:247
#2  0x00007ff631937a70 in hash_index_entry (istate=0x3dfb00d0400, ce=0x3dfb5c58bc8) at name-hash.c:122
#3  0x00007ff631938a2f in add_name_hash (istate=0x3dfb00d0400, ce=0x3dfb5c58bc8) at name-hash.c:638
#4  0x00007ff631a064de in set_index_entry (istate=0x3dfb00d0400, nr=8291, ce=0x3dfb5c58bc8) at sparse-index.c:255
#5  0x00007ff631a06692 in add_path_to_index (oid=0x5ff130, base=0x5ff580, path=0x3dfb4b725da "<redacted>", mode=33188, context=0x5ff570)    at sparse-index.c:307
#6  0x00007ff631a3b48c in read_tree_at (r=0x7ff631c026a0 <the_repo>, tree=0x3dfb5b41f60, base=0x5ff580, depth=2, pathspec=0x5ff5a0,    fn=0x7ff631a064e5 <add_path_to_index>, context=0x5ff570) at tree.c:46
#7  0x00007ff631a3b60b in read_tree_at (r=0x7ff631c026a0 <the_repo>, tree=0x3dfb5b41e80, base=0x5ff580, depth=1, pathspec=0x5ff5a0,    fn=0x7ff631a064e5 <add_path_to_index>, context=0x5ff570) at tree.c:80
#8  0x00007ff631a3b60b in read_tree_at (r=0x7ff631c026a0 <the_repo>, tree=0x3dfb5b41ac8, base=0x5ff580, depth=0, pathspec=0x5ff5a0,    fn=0x7ff631a064e5 <add_path_to_index>, context=0x5ff570) at tree.c:80
#9  0x00007ff631a06a95 in expand_index (istate=0x3dfb00d0100, pl=0x0) at sparse-index.c:422
#10 0x00007ff631a06cbd in ensure_full_index (istate=0x3dfb00d0100) at sparse-index.c:456
#11 0x00007ff631990d08 in index_name_stage_pos (istate=0x3dfb00d0100, name=0x3dfb0020080 "algorithm/levenshtein", namelen=21, stage=0,    search_mode=EXPAND_SPARSE) at read-cache.c:556
#12 0x00007ff631990d6c in index_name_pos (istate=0x3dfb00d0100, name=0x3dfb0020080 "algorithm/levenshtein", namelen=21) at read-cache.c:566
#13 0x00007ff63180dbb5 in sanitize_paths (argc=185, argv=0x3dfb0030018, prefix=0x0, skip_checks=0) at builtin/sparse-checkout.c:756
#14 0x00007ff63180de50 in sparse_checkout_set (argc=185, argv=0x3dfb0030018, prefix=0x0) at builtin/sparse-checkout.c:860
#15 0x00007ff63180e6c5 in cmd_sparse_checkout (argc=186, argv=0x3dfb0030018, prefix=0x0) at builtin/sparse-checkout.c:1063
#16 0x00007ff6317234cb in run_builtin (p=0x7ff631ad9b38 <commands+2808>, argc=187, argv=0x3dfb0030018) at git.c:548
#17 0x00007ff6317239c0 in handle_builtin (argc=187, argv=0x3dfb0030018) at git.c:808
#18 0x00007ff631723c7d in run_argv (argcp=0x5ffdd0, argv=0x5ffd78) at git.c:877
#19 0x00007ff6317241d1 in cmd_main (argc=187, argv=0x3dfb0030018) at git.c:1017
#20 0x00007ff631838b60 in main (argc=190, argv=0x3dfb0030000) at common-main.c:64 
```

The very bottom of the stack being the `rehash()` method from
`hashmap.c` as called within the `name-hash` API made me look at where
these hashmaps were being used in the sparse index logic. These were
being copied across indexes, which seems dangerous. Indeed, clearing
these hashmaps and setting them as not initialized fixes the segfault.

The second commit is a response to a test failure that happens in
`t1092-sparse-checkout-compatibility.sh` where `git stash pop` starts to
fail because the underlying `git checkout-index` process fails due to
colliding files. Passing the `-f` flag appears to work, but it's unclear
why this name-hash change causes that change in behavior.
dscho added a commit that referenced this pull request Oct 9, 2024
An internal customer reported a segfault when running `git
sparse-checkout set` with the `index.sparse` config enabled. I was
unable to reproduce it locally, but with their help we debugged into the
failing process and discovered the following stacktrace:

```
#0  0x00007ff6318fb7b0 in rehash (map=0x3dfb00d0440, newsize=1048576) at hashmap.c:125
#1  0x00007ff6318fbc66 in hashmap_add (map=0x3dfb00d0440, entry=0x3dfb5c58bc8) at hashmap.c:247
#2  0x00007ff631937a70 in hash_index_entry (istate=0x3dfb00d0400, ce=0x3dfb5c58bc8) at name-hash.c:122
#3  0x00007ff631938a2f in add_name_hash (istate=0x3dfb00d0400, ce=0x3dfb5c58bc8) at name-hash.c:638
#4  0x00007ff631a064de in set_index_entry (istate=0x3dfb00d0400, nr=8291, ce=0x3dfb5c58bc8) at sparse-index.c:255
#5  0x00007ff631a06692 in add_path_to_index (oid=0x5ff130, base=0x5ff580, path=0x3dfb4b725da "<redacted>", mode=33188, context=0x5ff570)    at sparse-index.c:307
#6  0x00007ff631a3b48c in read_tree_at (r=0x7ff631c026a0 <the_repo>, tree=0x3dfb5b41f60, base=0x5ff580, depth=2, pathspec=0x5ff5a0,    fn=0x7ff631a064e5 <add_path_to_index>, context=0x5ff570) at tree.c:46
#7  0x00007ff631a3b60b in read_tree_at (r=0x7ff631c026a0 <the_repo>, tree=0x3dfb5b41e80, base=0x5ff580, depth=1, pathspec=0x5ff5a0,    fn=0x7ff631a064e5 <add_path_to_index>, context=0x5ff570) at tree.c:80
#8  0x00007ff631a3b60b in read_tree_at (r=0x7ff631c026a0 <the_repo>, tree=0x3dfb5b41ac8, base=0x5ff580, depth=0, pathspec=0x5ff5a0,    fn=0x7ff631a064e5 <add_path_to_index>, context=0x5ff570) at tree.c:80
#9  0x00007ff631a06a95 in expand_index (istate=0x3dfb00d0100, pl=0x0) at sparse-index.c:422
#10 0x00007ff631a06cbd in ensure_full_index (istate=0x3dfb00d0100) at sparse-index.c:456
#11 0x00007ff631990d08 in index_name_stage_pos (istate=0x3dfb00d0100, name=0x3dfb0020080 "algorithm/levenshtein", namelen=21, stage=0,    search_mode=EXPAND_SPARSE) at read-cache.c:556
#12 0x00007ff631990d6c in index_name_pos (istate=0x3dfb00d0100, name=0x3dfb0020080 "algorithm/levenshtein", namelen=21) at read-cache.c:566
#13 0x00007ff63180dbb5 in sanitize_paths (argc=185, argv=0x3dfb0030018, prefix=0x0, skip_checks=0) at builtin/sparse-checkout.c:756
#14 0x00007ff63180de50 in sparse_checkout_set (argc=185, argv=0x3dfb0030018, prefix=0x0) at builtin/sparse-checkout.c:860
#15 0x00007ff63180e6c5 in cmd_sparse_checkout (argc=186, argv=0x3dfb0030018, prefix=0x0) at builtin/sparse-checkout.c:1063
#16 0x00007ff6317234cb in run_builtin (p=0x7ff631ad9b38 <commands+2808>, argc=187, argv=0x3dfb0030018) at git.c:548
#17 0x00007ff6317239c0 in handle_builtin (argc=187, argv=0x3dfb0030018) at git.c:808
#18 0x00007ff631723c7d in run_argv (argcp=0x5ffdd0, argv=0x5ffd78) at git.c:877
#19 0x00007ff6317241d1 in cmd_main (argc=187, argv=0x3dfb0030018) at git.c:1017
#20 0x00007ff631838b60 in main (argc=190, argv=0x3dfb0030000) at common-main.c:64 
```

The very bottom of the stack being the `rehash()` method from
`hashmap.c` as called within the `name-hash` API made me look at where
these hashmaps were being used in the sparse index logic. These were
being copied across indexes, which seems dangerous. Indeed, clearing
these hashmaps and setting them as not initialized fixes the segfault.

The second commit is a response to a test failure that happens in
`t1092-sparse-checkout-compatibility.sh` where `git stash pop` starts to
fail because the underlying `git checkout-index` process fails due to
colliding files. Passing the `-f` flag appears to work, but it's unclear
why this name-hash change causes that change in behavior.
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