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When running Git commands quickly -- such as in a shell script or the
test suite -- the Git commands frequently complete and start again
during the same second. The example fsmonitor hooks to integrate with
Watchman truncate the nanosecond times to seconds. In principle, this is
fine, as Watchman claims to use inclusive comparisons [1]. The result
should only be an over-representation of the changed paths since the
last Git command.
However, Watchman's own documentation claims "Using a timestamp is prone
to race conditions in understanding the complete state of the file tree"
[2]. All of their documented examples use a "clockspec" that looks like
'c:123:234'. Git should eventually learn how to store this type of
string to provide a stronger integration, but that will be a more
invasive change.
When using GIT_TEST_FSMONITOR="$(pwd)/t7519/fsmonitor-watchman", scripts
such as t7519-wtstatus.sh fail due to these race conditions. In fact,
running any test script with GIT_TEST_FSMONITOR pointing at
t/t7519/fsmonitor-wathcman will cause failures in the test_commit
function. The 'git add "$indir$file"' command fails due to not enough
time between the creation of '$file' and the 'git add' command.
For now, subtract one second from the timestamp we pass to Watchman.
This will make our window large enough to avoid these race conditions.
Increasing the window causes tests like t7519-wtstatus.sh to pass.
When the integration was introduced in def437671 (fsmonitor: add a
sample integration script for Watchman, 2018-09-22), the query included
an expression that would ignore files created and deleted in that
window. The performance reason for this change was to ignore temporary
files created by a build between Git commands. However, this causes
failures in script scenarios where Git is creating or deleting files
quickly.
When using GIT_TEST_FSMONITOR as before, t2203-add-intent.sh fails
due to this add-and-delete race condition.
By removing the "expression" from the Watchman query, we remove this
race condition. It will lead to some performance degradation in the case
of users creating and deleting temporary files inside their working
directory between Git commands. However, that is a cost we need to pay
to be correct.
[1] https://github.com/facebook/watchman/blob/master/query/since.cpp#L35-L39
[2] https://facebook.github.io/watchman/docs/clockspec.html
Helped-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Kevin Willford <Kevin.Willford@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Simplify and speed up the process of finding the git worktree when
running on Windows by keeping it in perl and avoiding spawning helper
processes.
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Though the process has chdir'd to the root of the working tree, the
PWD environment variable is only guaranteed to be updated accordingly
if a shell is involved -- which is not guaranteed to be the case.
That is, if `/usr/bin/perl` is a binary, $ENV{PWD} is unchanged from
whatever spawned `git` -- if `/usr/bin/perl` is a trivial shell
wrapper to the real `perl`, `$ENV{PWD}` will have been updated to the
root of the working copy.
Update to read from the Cwd module using the `getcwd` syscall, not the
PWD environment variable. The Cygwin case is left unchanged, as it
necessarily _does_ go through a shell.
Signed-off-by: Alex Vandiver <alexmv@dropbox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This provides modest performance savings. Benchmarking with the
following program, with and without `--no-pretty`, we find savings of
23% (0.316s -> 0.242s) in the git repository, and savings of 8% (5.24s
-> 4.86s) on a large repository with 580k files in the working copy.
#!/usr/bin/perl
use strict;
use warnings;
use IPC::Open2;
use JSON::XS;
my $pid = open2(\*CHLD_OUT, \*CHLD_IN, "watchman -j @ARGV")
or die "open2() failed: $!\n" .
"Falling back to scanning...\n";
my $query = qq|["query", "$ENV{PWD}", {}]|;
print CHLD_IN $query;
close CHLD_IN;
my $response = do {local $/; <CHLD_OUT>};
JSON::XS->new->utf8->decode($response);
Signed-off-by: Alex Vandiver <alexmv@dropbox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In Perl, setting $/ sets the string that is used as the "record
separator," which sets the boundary that the `<>` construct reads to.
Setting `local $/ = 0666;` evaluates the octal, getting 438, and
stringifies it. Thus, the later read from `<CHLD_OUT>` stops as soon
as it encounters the string "438" in the watchman output, yielding
invalid JSON; repositories containing filenames with SHA1 hashes are
able to trip this easily.
Set `$/` to undefined, thus slurping all output from watchman. Also
close STDIN which is provided to watchman, to better guarantee that we
cannot deadlock with watchman while both attempting to read.
Signed-off-by: Alex Vandiver <alexmv@dropbox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Instead of just taking $ENV{'PWD'}, use the same logic that converts
PWD to $git_work_tree on MSYS_NT in the watchman integration hook
script also on MINGW.
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This script integrates the new fsmonitor capabilities of git with the
cross platform Watchman file watching service. To use the script:
Download and install Watchman from https://facebook.github.io/watchman/.
Rename the sample integration hook from fsmonitor-watchman.sample to
fsmonitor-watchman. Configure git to use the extension:
git config core.fsmonitor .git/hooks/fsmonitor-watchman
Optionally turn on the untracked cache for optimal performance.
Signed-off-by: Ben Peart <benpeart@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Christian Couder <christian.couder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Kevin Willford
Ben Peart
Alex Vandiver