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Several tests wanted to verify that files were actually modified by a
merge, which it would do by checking that the mtime was updated. In
order to avoid problems with the merge completing so fast that the mtime
at the beginning and end of the operation was the same, these tests
would first set the mtime of a file to something "old". This "old"
value was usually determined as current system clock minus one second,
truncated to the nearest integer. Unfortunately, it appears the system
clock and filesystem clock are different and comparing across the two
runs into race problems resulting in flaky tests.
From https://stackoverflow.com/questions/14392975/timestamp-accuracy-on-ext4-sub-millsecond:
date will call the gettimeofday system call which will always return
the most accurate time available based on the cached kernel time,
adjusted by the CPU cycle time if available to give nanosecond
resolution. The timestamps stored in the file system however, are
only based on the cached kernel time. ie The time calculated at the
last timer interrupt.
and from https://apenwarr.ca/log/20181113:
Does mtime get set to >= the current time?
No, this depends on clock granularity. For example, gettimeofday()
can return times in microseconds on my system, but ext4 rounds
timestamps down to the previous ~10ms (but not exactly 10ms)
increment, with the surprising result that a newly-created file is
almost always created in the past:
$ python -c "
import os, time
t0 = time.time()
open('testfile', 'w').close()
print os.stat('testfile').st_mtime - t0
"
-0.00234484672546
So, instead of trying to compare across what are effectively two
different clocks, just avoid using the system clock. Any new updates to
files have to give an mtime at least as big as what is already in the
file, so we could define "old" as one second before the mtime found in
the file before the merge starts. But, to avoid problems with leap
seconds, ntp updates, filesystems that only provide two second
resolution, and other such weirdness, let's just pick an hour before the
mtime found in the file before the merge starts.
Also, clarify in one test where we check the mtime of different files
that it really was intentional. I totally forgot the reasons for that
and assumed it was a bug when asked.
Reported-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In t6022, we were testing for file being overwritten (or not) based on
an output message instead of checking for the file being overwritten.
Since we can check for the file being overwritten via mtime updates,
check that instead.
In t6046, we were largely checking for both the expected behavior and a
proxy for it, which is unnecessary. The calls to test-tool also were a
bit cryptic. Make them a little clearer.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Transform the setup "tests" to setup functions, and have the actual
tests call the setup functions. Advantages:
* Should make life easier for people working with webby CI/PR builds
who have to abuse mice (and their own index finger as well) in
order to switch from viewing one testcase to another. Sounds
awful; hopefully this will improve things for them.
* Improves re-runnability: any failed test in any of these three
files can now be re-run in isolation, e.g.
./t6042* --ver --imm -x --run=21
whereas before it would require two tests to be specified to the
--run argument, the other needing to be picked out as the relevant
setup test from one or two tests before.
* Importantly, this still keeps the "setup" and "test" sections
somewhat separate to make it easier for readers to discern what is
just ancillary setup and what the intent of the test is.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When all of x/a, x/b, and x/c have moved to z/a, z/b, and z/c on one
branch, there is a question about whether x/d added on a different
branch should remain at x/d or appear at z/d when the two branches are
merged. There are different possible viewpoints here:
A) The file was placed at x/d; it's unrelated to the other files in
x/ so it doesn't matter that all the files from x/ moved to z/ on
one branch; x/d should still remain at x/d.
B) x/d is related to the other files in x/, and x/ was renamed to z/;
therefore x/d should be moved to z/d.
Since there was no ability to detect directory renames prior to
git-2.18, users experienced (A) regardless of context. Choice (B) was
implemented in git-2.18, with no option to go back to (A), and has been
in use since. However, one user reported that the merge results did not
match their expectations, making the change of default problematic,
especially since there was no notice printed when directory rename
detection moved files.
Note that there is also a third possibility here:
C) There are different answers depending on the context and content
that cannot be determined by git, so this is a conflict. Use a
higher stage in the index to record the conflict and notify the
user of the potential issue instead of silently selecting a
resolution for them.
Add an option for users to specify their preference for whether to use
directory rename detection, and default to (C). Even when directory
rename detection is on, add notice messages about files moved into new
directories.
As a sidenote, x/d did not have to be a new file here; it could have
already existed at some other path and been renamed to x/d, with
directory rename detection just renaming it again to z/d. Thus, it's
not just new files, but also a modification to all rename types (normal
renames, rename/add, rename/delete, rename/rename(1to1),
rename/rename(1to2), and rename/rename(2to1)).
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Unlike "FOO=bar cmd" one-shot environment variable assignments
which exist only for the invocation of 'cmd', those assigned by
"FOO=bar shell_func" exist within the running shell and continue to
do so until the process exits (or are explicitly unset). It is
unlikely that this behavior was intended by the test author.
In these particular tests, the "FOO=bar shell_func" invocations are
already in subshells, so the assignments don't last too long, don't
appear to harm subsequent commands in the same subshells, and don't
affect other tests in the same scripts, however, the usage is
nevertheless misleading and poor practice, so fix the tests to assign
and export the environment variables in the usual fashion.
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The can-working-tree-updates-be-skipped check has had a long and blemished
history. The update can be skipped iff:
a) The merge is clean
b) The merge matches what was in HEAD (content, mode, pathname)
c) The target path is usable (i.e. not involved in D/F conflict)
Traditionally, we split b into parts:
b1) The merged result matches the content and mode found in HEAD
b2) The merged target path existed in HEAD
Steps a & b1 are easy to check; we have always gotten those right. While
it is easy to overlook step c, this was fixed seven years ago with commit
4ab9a157d069 ("merge_content(): Check whether D/F conflicts are still
present", 2010-09-20). merge-recursive didn't have a readily available
way to directly check step b2, so various approximations were used:
* In commit b2c8c0a76274 ("merge-recursive: When we detect we can skip
an update, actually skip it", 2011-02-28), it was noted that although
the code claimed it was skipping the update, it did not actually skip
the update. The code was made to skip it, but used lstat(path, ...)
as an approximation to path-was-tracked-in-index-before-merge.
* In commit 5b448b853030 ("merge-recursive: When we detect we can skip
an update, actually skip it", 2011-08-11), the problem with using
lstat was noted. It was changed to the approximation
path2 && strcmp(path, path2)
which is also wrong. !path2 || strcmp(path, path2) would have been
better, but would have fallen short with directory renames.
* In c5b761fb2711 ("merge-recursive: ensure we write updates for
directory-renamed file", 2018-02-14), the problem with the previous
approximation was noted and changed to
was_tracked(path)
That looks close to what we were trying to answer, but was_tracked()
as implemented at the time should have been named is_tracked(); it
returned something different than what we were looking for.
* To make matters more complex, fixing was_tracked() isn't sufficient
because the splitting of b into b1 and b2 is wrong. Consider the
following merge with a rename/add conflict:
side A: modify foo, add unrelated bar
side B: rename foo->bar (but don't modify the mode or contents)
In this case, the three-way merge of original foo, A's foo, and B's
bar will result in a desired pathname of bar with the same
mode/contents that A had for foo. Thus, A had the right mode and
contents for the file, and it had the right pathname present (namely,
bar), but the bar that was present was unrelated to the contents, so
the working tree update was not skippable.
Fix this by introducing a new function:
was_tracked_and_matches(o, path, &mfi.oid, mfi.mode)
and use it to directly check for condition b.
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Add several tests checking whether updates can be skipped in a merge.
Also add several similar testcases for where updates cannot be skipped in
a merge to make sure that we skip if and only if we should.
In particular:
* Testcase 1a (particularly 1a-check-L) would have pointed out the
problem Linus has been dealing with for year with his merges[1].
* Testcase 2a (particularly 2a-check-L) would have pointed out the
problem with my directory-rename-series before it broke master[2].
* Testcases 3[ab] (particularly 3a-check-L) provide a simpler testcase
than 12b of t6043 making that one easier to understand.
* There are several complementary testcases to make sure we're not just
fixing those particular issues while regressing in the opposite
direction.
* There are also a pair of tests for the special case when a merge
results in a skippable update AND the user has dirty modifications to
the path.
[1] https://public-inbox.org/git/CA+55aFzLZ3UkG5svqZwSnhNk75=fXJRkvU1m_RHBG54NOoaZPA@mail.gmail.com/
[2] https://public-inbox.org/git/xmqqmuya43cs.fsf@gitster-ct.c.googlers.com/
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Elijah Newren
Eric Sunshine