When merging a signed tag fmt-merge-msg was unable to verify its
validity missing the necessary ssh allowedSignersFile config.
Adds gpg config parsing to fmt-merge-msg.
Adds tests for ssh signed tags to fmt-merge-msg tests.
Signed-off-by: Fabian Stelzer <fs@gigacodes.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* fs/ssh-signing:
ssh signing: test that gpg fails for unknown keys
ssh signing: tests for logs, tags & push certs
ssh signing: duplicate t7510 tests for commits
ssh signing: verify signatures using ssh-keygen
ssh signing: provide a textual signing_key_id
ssh signing: retrieve a default key from ssh-agent
ssh signing: add ssh key format and signing code
ssh signing: add test prereqs
ssh signing: preliminary refactoring and clean-up
Code clean-up in "git difftool".
* da/difftool:
difftool: add a missing space to the run_dir_diff() comments
difftool: remove an unnecessary call to strbuf_release()
difftool: refactor dir-diff to write files using helper functions
difftool: create a tmpdir path without repeated slashes
CI learns to run the leak sanitizer builds.
* ab/sanitize-leak-ci:
tests: add a test mode for SANITIZE=leak, run it in CI
Makefile: add SANITIZE=leak flag to GIT-BUILD-OPTIONS
The ref iteration code used to optionally allow dangling refs to be
shown, which has been tightened up.
* jk/ref-paranoia:
refs: drop "broken" flag from for_each_fullref_in()
ref-filter: drop broken-ref code entirely
ref-filter: stop setting FILTER_REFS_INCLUDE_BROKEN
repack, prune: drop GIT_REF_PARANOIA settings
refs: turn on GIT_REF_PARANOIA by default
refs: omit dangling symrefs when using GIT_REF_PARANOIA
refs: add DO_FOR_EACH_OMIT_DANGLING_SYMREFS flag
refs-internal.h: reorganize DO_FOR_EACH_* flag documentation
refs-internal.h: move DO_FOR_EACH_* flags next to each other
t5312: be more assertive about command failure
t5312: test non-destructive repack
t5312: create bogus ref as necessary
t5312: drop "verbose" helper
t5600: provide detached HEAD for corruption failures
t5516: don't use HEAD ref for invalid ref-deletion tests
t7900: clean up some more broken refs
Test updates.
* sg/test-split-index-fix:
read-cache: fix GIT_TEST_SPLIT_INDEX
tests: disable GIT_TEST_SPLIT_INDEX for sparse index tests
read-cache: look for shared index files next to the index, too
t1600-index: disable GIT_TEST_SPLIT_INDEX
t1600-index: don't run git commands upstream of a pipe
t1600-index: remove unnecessary redirection
"git multi-pack-index write --bitmap" learns to propagate the
hashcache from original bitmap to resulting bitmap.
* tb/midx-write-propagate-namehash:
t5326: test propagating hashcache values
p5326: generate pack bitmaps before writing the MIDX bitmap
p5326: don't set core.multiPackIndex unnecessarily
p5326: create missing 'perf-tag' tag
midx.c: respect 'pack.writeBitmapHashcache' when writing bitmaps
pack-bitmap.c: propagate namehash values from existing bitmaps
t/helper/test-bitmap.c: add 'dump-hashes' mode
Code cleanup.
* ab/repo-settings-cleanup:
repository.h: don't use a mix of int and bitfields
repo-settings.c: simplify the setup
read-cache & fetch-negotiator: check "enum" values in switch()
environment.c: remove test-specific "ignore_untracked..." variable
wrapper.c: add x{un,}setenv(), and use xsetenv() in environment.c
Regression in "git commit-graph" command line parsing has been
corrected.
* tb/commit-graph-usage-fix:
builtin/multi-pack-index.c: disable top-level --[no-]progress
builtin/commit-graph.c: don't accept common --[no-]progress
"git rebase <upstream> <tag>" failed when aborted in the middle, as
it mistakenly tried to write the tag object instead of peeling it
to HEAD.
* pw/rebase-of-a-tag-fix:
rebase: dereference tags
rebase: use lookup_commit_reference_by_name()
rebase: use our standard error return value
t3407: rework rebase --quit tests
t3407: strengthen rebase --abort tests
t3407: use test_path_is_missing
t3407: rename a variable
t3407: use test_cmp_rev
t3407: use test_commit
t3407: run tests in $TEST_DIRECTORY
More code paths that use the hack to add submodule's object
database to the set of alternate object store have been cleaned up.
* jt/add-submodule-odb-clean-up:
revision: remove "submodule" from opt struct
repository: support unabsorbed in repo_submodule_init
submodule: remove unnecessary unabsorbed fallback
When using `test_size` with `wc -c`, users on certain platforms can run
into issues when `wc` emits leading space characters in its output,
which confuses get_times.
Callers could switch to use test_file_size instead of `wc -c` (the
former never prints leading space characters, so will always work with
test_size regardless of platform), but this is an easy enough spot to
miss that we should teach get_times to be more tolerant of the input it
accepts.
Teach get_times to do just that by stripping any leading space
characters.
Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
b3dfeebb92 (rebase: avoid computing unnecessary patch IDs, 2016-07-29)
added a perf test that calls tac(1) from GNU core utilities. Support
systems without it by reversing the generated list using sort -nr
instead. sort(1) with options -n and -r is already used in other tests.
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Protocol v0 clients can get stuck parsing a malformed feature line.
* ah/connect-parse-feature-v0-fix:
connect: also update offset for features without values
Sensitive data in the HTTP trace were supposed to be redacted, but
we failed to do so in HTTP/2 requests.
* jk/http-redact-fix:
http: match headers case-insensitively when redacting
"git cvsserver" had a long-standing bug in its authentication code,
which has finally been corrected (it is unclear and is a separate
question if anybody is seriously using it, though).
* cb/cvsserver:
Documentation: cleanup git-cvsserver
git-cvsserver: protect against NULL in crypt(3)
git-cvsserver: use crypt correctly to compare password hashes
"git clone" from a repository whose HEAD is unborn into a bare
repository didn't follow the branch name the other side used, which
is corrected.
* jk/clone-unborn-head-in-bare:
clone: handle unborn branch in bare repos
"git stash", where the tentative change involves changing a
directory to a file (or vice versa), was confused, which has been
corrected.
* en/stash-df-fix:
stash: restore untracked files AFTER restoring tracked files
stash: avoid feeding directories to update-index
t3903: document a pair of directory/file bugs
The paths generated by difftool are passed to user-facing diff tools.
Using paths with repeated slashes in them is a cosmetic blemish that
is exposed to users and can be avoided.
Use a strbuf to create the buffer used for the dir-diff tmpdir.
Strip trailing slashes from the value read from TMPDIR to avoid
repeated slashes in the generated paths.
Adjust the error handling to avoid leaking strbufs and to avoid
returning -1 to cmd_main().
Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Code cleanup to limit memory consumption and tighten protocol
message parsing.
* jk/reduce-malloc-in-v2-servers:
ls-refs: reject unknown arguments
serve: reject commands used as capabilities
serve: reject bogus v2 "command=ls-refs=foo"
docs/protocol-v2: clarify some ls-refs ref-prefix details
ls-refs: ignore very long ref-prefix counts
serve: drop "keys" strvec
serve: provide "receive" function for session-id capability
serve: provide "receive" function for object-format capability
serve: add "receive" method for v2 capabilities table
serve: return capability "value" from get_capability()
serve: rename is_command() to parse_command()
Commit b681b191 introduced the support of systemd timers for git
maintenance.
A test is leveraging the `systemd-analyze verify` utility to verify the
correctness of the systemd unit files generated by git.
But on some systems, although the `systemd-analyze` tool is installed
and supports the `verify` subcommand, it fails with some permission
errors.
So, instead of only checking if the `verify` subcommand exists, a more
reliable way of detecting whether `systemd-analyze verify` can be used
is to try to use it.
The SYSTEMD_ANALYZE prerequisite is now trying to run `systemd-analyze
verify` on a systemd unit file which is shipped by systemd itself.
We can reasonably think that, on systemd hosts, this file is present and
valid.
Signed-off-by: Lénaïc Huard <lenaic@lhuard.fr>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Move various *_INIT macros to use designated initializers. This helps
readability. I've only picked those leftover macros that were not
touched by another in-flight series of mine which changed others, but
also how initialization was done.
In the case of SUBMODULE_ALTERNATE_SETUP_INIT I've left an explicit
initialization of "error_mode", even though
SUBMODULE_ALTERNATE_ERROR_IGNORE itself is defined as "0". Let's not
peek under the hood and assume that enum fields we know the value of
will stay at "0".
The change to "TESTSUITE_INIT" in "t/helper/test-run-command.c" was
part of an earlier on-list version[1] of c90be786da (test-tool
run-command: fix flip-flop init pattern, 2021-09-11).
1. https://lore.kernel.org/git/patch-1.1-0aa4523ab6e-20210909T130849Z-avarab@gmail.com/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Change the initialization of "struct strbuf" changed in
cbc0f81d96 (strbuf: use designated initializers in STRBUF_INIT,
2017-07-10) to omit specifying "alloc" and "len", as we do with other
"alloc" and "len" (or "nr") in similar structs.
Let's likewise omit the explicit initialization of all fields in the
"struct ipc_client_connect_option" struct added in
59c7b88198 (simple-ipc: add win32 implementation, 2021-03-15).
Do the same for a few other initializers, e.g. STRVEC_INIT and
CACHE_DEF_INIT.
Finally, start incrementally changing the same pattern in
"t/helper/test-run-command.c". This change was part of an earlier
on-list version[1] of c90be786da (test-tool run-command: fix
flip-flop init pattern, 2021-09-11).
1. https://lore.kernel.org/git/patch-1.1-0aa4523ab6e-20210909T130849Z-avarab@gmail.com/
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Of the ref-filter callers, for-each-ref and git-branch both set the
INCLUDE_BROKEN flag (but git-tag does not, which is a weird
inconsistency). But now that GIT_REF_PARANOIA is on by default, that
produces almost the same outcome for all three.
The one exception is that GIT_REF_PARANOIA will omit dangling symrefs.
That's a better behavior for these tools, as they would never include
such a symref in the main output anyway (they can't, as it doesn't point
to an object). Instead they issue a warning to stderr. But that warning
is somewhat useless; a dangling symref is a perfectly reasonable thing
to have in your repository, and is not a sign of corruption. It's much
friendlier to just quietly ignore it.
And in terms of robustness, the warning gains us little. It does not
impact the exit code of either tool. So while the warning _might_ clue
in a user that they have an unexpected broken symref, it would not help
any kind of scripted use.
This patch converts for-each-ref and git-branch to stop using the
INCLUDE_BROKEN flag. That gives them more reasonable behavior, and
harmonizes them with git-tag.
We have to change one test to adapt to the situation. t1430 tries to
trigger all of the REF_ISBROKEN behaviors from the underlying ref code.
It uses for-each-ref to do so (because there isn't any other mechanism).
That will no longer issue a warning about the symref which points to an
invalid name, as it's considered dangling (and we can instead be sure
that it's _not_ mentioned on stderr). Note that we do still complain
about the illegally named "broken..symref"; its problem is not that it's
dangling, but the name of the symref itself is illegal.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The original point of the GIT_REF_PARANOIA flag was to include broken
refs in iterations, so that possibly-destructive operations would not
silently ignore them (and would generally instead try to operate on the
oids and fail when the objects could not be accessed).
We already turned this on by default for some dangerous operations, like
"repack -ad" (where missing a reachability tip would mean dropping the
associated history). But it was not on for general use, even though it
could easily result in the spreading of corruption (e.g., imagine
cloning a repository which simply omits some of its refs because
their objects are missing; the result quietly succeeds even though you
did not clone everything!).
This patch turns on GIT_REF_PARANOIA by default. So a clone as mentioned
above would actually fail (upload-pack tells us about the broken ref,
and when we ask for the objects, pack-objects fails to deliver them).
This may be inconvenient when working with a corrupted repository, but:
- we are better off to err on the side of complaining about
corruption, and then provide mechanisms for explicitly loosening
safety.
- this is only one type of corruption anyway. If we are missing any
other objects in the history that _aren't_ ref tips, then we'd
behave similarly (happily show the ref, but then barf when we
started traversing).
We retain the GIT_REF_PARANOIA variable, but simply default it to "1"
instead of "0". That gives the user an escape hatch for loosening this
when working with a corrupt repository. It won't work across a remote
connection to upload-pack (because we can't necessarily set environment
variables on the remote), but there the client has other options (e.g.,
choosing which refs to fetch).
As a bonus, this also makes ref iteration faster in general (because we
don't have to call has_object_file() for each ref), though probably not
noticeably so in the general case. In a repo with a million refs, it
shaved a few hundred milliseconds off of upload-pack's advertisement;
that's noticeable, but most repos are not nearly that large.
The possible downside here is that any operation which iterates refs but
doesn't ever open their objects may now quietly claim to have X when the
object is corrupted (e.g., "git rev-list new-branch --not --all" will
treat a broken ref as uninteresting). But again, that's not really any
different than corruption below the ref level. We might have
refs/heads/old-branch as non-corrupt, but we are not actively checking
that we have the entire reachable history. Or the pointed-to object
could even be corrupted on-disk (but our "do we have it" check would
still succeed). In that sense, this is merely bringing ref-corruption in
line with general object corruption.
One alternative implementation would be to actually check for broken
refs, and then _immediately die_ if we see any. That would cause the
"rev-list --not --all" case above to abort immediately. But in many ways
that's the worst of all worlds:
- it still spends time looking up the objects an extra time
- it still doesn't catch corruption below the ref level
- it's even more inconvenient; with the current implementation of
GIT_REF_PARANOIA for something like upload-pack, we can make
the advertisement and let the client choose a non-broken piece of
history. If we bail as soon as we see a broken ref, they cannot even
see the advertisement.
The test changes here show some of the fallout. A non-destructive "git
repack -adk" now fails by default (but we can override it). Deleting a
broken ref now actually tells the hooks the correct "before" state,
rather than a confusing null oid.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Dangling symrefs aren't actually a corruption problem. It's perfectly
fine for refs/remotes/origin/HEAD to point to an unborn branch. And in
particular, if you are trying to establish reachability, a symref that
points nowhere doesn't matter either way. Any ref it could point to will
be examined during the rest of the traversal.
It's possible that a symref pointing nowhere _could_ be a sign that the
ref it was meant to point to was deleted accidentally (e.g., via
corruption). But there is no particular reason to think that is true for
any given case, and in the meantime, GIT_REF_PARANOIA kicking in
automatically for some operations means they'll fail unnecessarily.
So let's loosen it just a bit. The new test in t5312 shows off an
example that is safe, but currently fails (and no longer does after this
patch).
Note that we don't do anything if the caller explicitly asked for
DO_FOR_EACH_INCLUDE_BROKEN. In that case they may be looking for
dangling symrefs themselves, and setting GIT_REF_PARANOIA should not
_loosen_ things from what the caller asked for.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When repacking or pruning in a corrupted repository, our tests in t5312
argue that it is OK to complete the operation or bail, as long as we
don't actually delete the objects pointed to by the corruption.
This isn't a wrong line of reasoning, but the tests are a bit permissive
by using test_might_fail. The fact is that we _do_ bail currently, and
if we ever stopped doing so, that would be worthy of a human
investigating. So let's switch these to test_must_fail.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In t5312, we create a state with a broken ref, and then make sure that
destructive repacks don't silently ignore the breakage (where a
destructive repack is one that might drop objects). But we don't check
the behavior of non-destructive repacks at all (i.e., ones where we'd
keep unreachable objects).
So let's add a test to confirm the current behavior, which is that
they are allowed (i.e., ignoring the breakage and considering any
objects it points to as unreachable). This may change in the future, but
we'd like for the test suite to alert us to that fact.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Some tests in t5312 create an illegally-named ref, and then see how
various operations handle it. But between those operations, we also do
some more setup (e.g., repacking), and we are subtly depending on how
those setup steps react to the illegal ref.
To future-proof us against those behaviors changing, let's instead
create and clean up our bogus ref on demand in the tests that need it.
This has two small extra advantages:
- the tests are more stand-alone; we do not need an extra test to clean
up the ref before moving on to other parts of the script
- the creation and cleanup is together in one helper function. Because
these depend on touching the refs in the filesystem directly, they
may need to be tweaked for a world with alternate backends (they have
not been noticed so far in the reftable work because with a non-file
backend the tests don't fail; they simply become uninteresting noops
because the broken ref isn't read at all).
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
t5312 has several uses of the "verbose" helper, as described in
8ad1652418 (t5304: use helper to report failure of "test foo = bar",
2014-10-10). Back then the "-x" trace option for tests was new, and was
not as pleasant to use (e.g., some tests failed under "-x", we did not
support BASH_XTRACEFD, etc).
These days it is clear that "-x" is the preferred way to get extra
output, and we don't need to mark up individual tests. Let's get rid of
the uses of "verbose" here, as one step toward eradicating it totally.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When checking how git-clone behaves when it fails, we stimulate some
failures by trying to do a clone from a local repository whose objects
have been removed. Because these clones use local optimizations, there's
a subtle dependency in how the corruption is handled on the sending
side.
If upload-pack does not show us the broken refs (which it does not
currently), then we see only HEAD (which is itself broken), and clone
that as a detached HEAD. When we try to write the ref, we notice that we
never got the object and bail.
But if upload-pack _does_ show us the broken refs (which it may in a
future patch), then we'll realize that HEAD is a symref and just write
that. You'd think we'd fail when writing out the refs themselves, but we
don't; we do a bulk write and skip the connectivity check because of our
--local optimizations. For the non-bare case, we do notice the problem
when we try to checkout. But for a bare repository, we unexpectedly
complete the clone successfully!
At first glance this may seem like a bug. But the whole point of those
local optimizations is to give up some safety for speed. If you want to
be careful, you should be using "--no-local", which would notice that
the pack did not transfer sufficient objects. We could do that in these
tests, but part of the point is for them to fail at specific moments
(and indeed, we have a later test that checks for transport failure).
However, we can make this less subtle and future-proof it against
changes on the upload-pack side by just having an explicit detached
HEAD in the corrupted repo. Now we'll fail as expected during the ref
write if any ref _or_ HEAD is corrupt, whether we're --bare or not.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A few tests in t5516 want to assert that we can delete a corrupted ref
whose pointed-to object is missing. They do so by using the "main"
branch, which is also pointed to by HEAD.
This does work, but only because of a subtle assumption about the
implementation. We do not block the deletion because of the invalid ref,
but we _also_ do not notice that the deleted branch is pointed to by
HEAD. And so the safety rule of "do not allow HEAD to be deleted in a
non-bare repository" does not kick in, and the test passes.
Let's instead use a non-HEAD branch. That still tests what we care about
here (deleting a corrupt ref), but without implicitly depending on our
failure to notice that we're deleting HEAD. That will future proof the
test against that behavior changing.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The "incremental-repack task" test replaces the object directory with a
known state. As a result, some of our refs point to objects that are not
included in that state.
Commit 3cf5f221be (t7900: clean up some broken refs, 2021-01-19) cleaned
up some of those (that were causing warnings to stderr from the
maintenance process). But there are a few more that were missed. These
aren't hurting anything for now, but it's certainly an unexpected state
to leave the test repository in, and it will become a problem if repack
ever gets more picky about broken refs.
Let's clean up those additional refs (which are all in refs/remotes,
with nothing there that isn't broken), and add an extra "for-each-ref"
call to assert that we've got everything.
Signed-off-by: Jeff King <peff@peff.net>
Reviewed-by: Jonathan Tan <jonathantanmy@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
parse_feature_value() takes an offset, and uses it to seek past the
point in features_list that we've already seen. However if the feature
being searched for does not specify a value, the offset is not
updated. Therefore if we call parse_feature_value() in a loop on a
value-less feature, we'll keep on parsing the same feature over and over
again. This usually isn't an issue: there's no point in using
next_server_feature_value() to search for repeated instances of the same
capability unless that capability typically specifies a value - but a
broken server could send a response that omits the value for a feature
even when we are expecting a value.
Therefore we add an offset update calculation for the no-value case,
which helps ensure that loops using next_server_feature_value() will
always terminate.
next_server_feature_value(), and the offset calculation, were first
added in 2.28 in 2c6a403d96 (connect: add function to parse multiple
v1 capability values, 2020-05-25).
Thanks to Peff for authoring the test.
Co-authored-by: Jeff King <peff@peff.net>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Andrzej Hunt <andrzej@ahunt.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The error in "git help no-such-git-command" is handled better.
* ma/help-w-check-for-requested-page:
help: make sure local html page exists before calling external processes
Adjust credential-cache helper to Windows.
* cb/unix-sockets-with-windows:
git-compat-util: include declaration for unix sockets in windows
credential-cache: check for windows specific errors
t0301: fixes for windows compatibility
An oddball OPTION_ARGUMENT feature has been removed from the
parse-options API.
* ab/retire-option-argument:
parse-options API: remove OPTION_ARGUMENT feature
difftool: use run_command() API in run_file_diff()
difftool: prepare "diff" cmdline in cmd_difftool()
difftool: prepare "struct child_process" in cmd_difftool()
Rewrite of "git bisect" in C continues.
* mr/bisect-in-c-4:
bisect--helper: retire `--bisect-next-check` subcommand
bisect--helper: reimplement `bisect_run` shell function in C
bisect--helper: reimplement `bisect_visualize()` shell function in C
run-command: make `exists_in_PATH()` non-static
t6030-bisect-porcelain: add test for bisect visualize
t6030-bisect-porcelain: add tests to control bisect run exit cases
Taking advantage of the CGI interface, http-backend has been
updated to enable protocol v2 automatically when the other side
asks for it.
* jk/http-server-protocol-versions:
docs/protocol-v2: point readers transport config discussion
docs/git: discuss server-side config for GIT_PROTOCOL
docs/http-backend: mention v2 protocol
http-backend: handle HTTP_GIT_PROTOCOL CGI variable
t5551: test v2-to-v0 http protocol fallback
When "git am --abort" fails to abort correctly, it still exited
with exit status of 0, which has been corrected.
* en/am-abort-fix:
am: fix incorrect exit status on am fail to abort
t4151: add a few am --abort tests
git-am.txt: clarify --abort behavior
