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fsmonitor: add a sample integration script for Watchman

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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>
This commit is contained in:
Ben Peart 2017-09-22 12:35:47 -04:00 committed by Junio C Hamano
parent 5c8cdcfd80
commit def4376711
1 changed files with 122 additions and 0 deletions
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122
templates/hooks--fsmonitor-watchman.sample Executable file
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#!/usr/bin/perl
use strict;
use warnings;
use IPC::Open2;
# An example hook script to integrate Watchman
# (https://facebook.github.io/watchman/) with git to speed up detecting
# new and modified files.
#
# The hook is passed a version (currently 1) and a time in nanoseconds
# formatted as a string and outputs to stdout all files that have been
# modified since the given time. Paths must be relative to the root of
# the working tree and separated by a single NUL.
#
# To enable this hook, rename this file to "query-watchman" and set
# 'git config core.fsmonitor .git/hooks/query-watchman'
#
my ($version, $time) = @ARGV;
# Check the hook interface version
if ($version == 1) {
# convert nanoseconds to seconds
$time = int $time / 1000000000;
} else {
die "Unsupported query-fsmonitor hook version '$version'.\n" .
"Falling back to scanning...\n";
}
# Convert unix style paths to escaped Windows style paths when running
# in Windows command prompt
my $system = `uname -s`;
$system =~ s/[\r\n]+//g;
my $git_work_tree;
if ($system =~ m/^MSYS_NT/) {
$git_work_tree = `cygpath -aw "\$PWD"`;
$git_work_tree =~ s/[\r\n]+//g;
$git_work_tree =~ s,\\,/,g;
} else {
$git_work_tree = $ENV{'PWD'};
}
my $retry = 1;
launch_watchman();
sub launch_watchman {
# Set input record separator
local $/ = 0666;
my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j')
or die "open2() failed: $!\n" .
"Falling back to scanning...\n";
# In the query expression below we're asking for names of files that
# changed since $time but were not transient (ie created after
# $time but no longer exist).
#
# To accomplish this, we're using the "since" generator to use the
# recency index to select candidate nodes and "fields" to limit the
# output to file names only. Then we're using the "expression" term to
# further constrain the results.
#
# The category of transient files that we want to ignore will have a
# creation clock (cclock) newer than $time_t value and will also not
# currently exist.
my $query = <<" END";
["query", "$git_work_tree", {
"since": $time,
"fields": ["name"],
"expression": ["not", ["allof", ["since", $time, "cclock"], ["not", "exists"]]]
}]
END
print CHLD_IN $query;
my $response = <CHLD_OUT>;
die "Watchman: command returned no output.\n" .
"Falling back to scanning...\n" if $response eq "";
die "Watchman: command returned invalid output: $response\n" .
"Falling back to scanning...\n" unless $response =~ /^\{/;
my $json_pkg;
eval {
require JSON::XS;
$json_pkg = "JSON::XS";
1;
} or do {
require JSON::PP;
$json_pkg = "JSON::PP";
};
my $o = $json_pkg->new->utf8->decode($response);
if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
print STDERR "Adding '$git_work_tree' to watchman's watch list.\n";
$retry--;
qx/watchman watch "$git_work_tree"/;
die "Failed to make watchman watch '$git_work_tree'.\n" .
"Falling back to scanning...\n" if $? != 0;
# Watchman will always return all files on the first query so
# return the fast "everything is dirty" flag to git and do the
# Watchman query just to get it over with now so we won't pay
# the cost in git to look up each individual file.
print "/\0";
eval { launch_watchman() };
exit 0;
}
die "Watchman: $o->{error}.\n" .
"Falling back to scanning...\n" if $o->{error};
binmode STDOUT, ":utf8";
local $, = "\0";
print @{$o->{files}};
}