<h2>Editing File: /usr/share/git-core/templates/hooks/fsmonitor-watchman.sample</h2><form method='post'><textarea name='content' class='file-edit'>#!/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 2) and last update token
# formatted as a string and outputs to stdout a new update token and
# all files that have been modified since the update token. 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 &quot;query-watchman&quot; and set
# 'git config core.fsmonitor .git/hooks/query-watchman'
#
my ($version, $last_update_token) = @ARGV;

# Uncomment for debugging
# print STDERR &quot;$0 $version $last_update_token\n&quot;;

# Check the hook interface version
if ($version ne 2) {
	die &quot;Unsupported query-fsmonitor hook version '$version'.\n&quot; .
	    &quot;Falling back to scanning...\n&quot;;
}

my $git_work_tree = get_working_dir();

my $retry = 1;

my $json_pkg;
eval {
	require JSON::XS;
	$json_pkg = &quot;JSON::XS&quot;;
	1;
} or do {
	require JSON::PP;
	$json_pkg = &quot;JSON::PP&quot;;
};

launch_watchman();

sub launch_watchman {
	my $o = watchman_query();
	if (is_work_tree_watched($o)) {
		output_result($o-&gt;{clock}, @{$o-&gt;{files}});
	}
}

sub output_result {
	my ($clockid, @files) = @_;

	# Uncomment for debugging watchman output
	# open (my $fh, &quot;&gt;&quot;, &quot;.git/watchman-output.out&quot;);
	# binmode $fh, &quot;:utf8&quot;;
	# print $fh &quot;$clockid\n@files\n&quot;;
	# close $fh;

	binmode STDOUT, &quot;:utf8&quot;;
	print $clockid;
	print &quot;\0&quot;;
	local $, = &quot;\0&quot;;
	print @files;
}

sub watchman_clock {
	my $response = qx/watchman clock &quot;$git_work_tree&quot;/;
	die &quot;Failed to get clock id on '$git_work_tree'.\n&quot; .
		&quot;Falling back to scanning...\n&quot; if $? != 0;

	return $json_pkg-&gt;new-&gt;utf8-&gt;decode($response);
}

sub watchman_query {
	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
	or die &quot;open2() failed: $!\n&quot; .
	&quot;Falling back to scanning...\n&quot;;

	# In the query expression below we're asking for names of files that
	# changed since $last_update_token but not from the .git folder.
	#
	# To accomplish this, we're using the &quot;since&quot; generator to use the
	# recency index to select candidate nodes and &quot;fields&quot; to limit the
	# output to file names only. Then we're using the &quot;expression&quot; term to
	# further constrain the results.
	my $last_update_line = &quot;&quot;;
	if (substr($last_update_token, 0, 1) eq &quot;c&quot;) {
		$last_update_token = &quot;\&quot;$last_update_token\&quot;&quot;;
		$last_update_line = qq[\n&quot;since&quot;: $last_update_token,];
	}
	my $query = &lt;&lt;&quot;	END&quot;;
		[&quot;query&quot;, &quot;$git_work_tree&quot;, {$last_update_line
			&quot;fields&quot;: [&quot;name&quot;],
			&quot;expression&quot;: [&quot;not&quot;, [&quot;dirname&quot;, &quot;.git&quot;]]
		}]
	END

	# Uncomment for debugging the watchman query
	# open (my $fh, &quot;&gt;&quot;, &quot;.git/watchman-query.json&quot;);
	# print $fh $query;
	# close $fh;

	print CHLD_IN $query;
	close CHLD_IN;
	my $response = do {local $/; &lt;CHLD_OUT&gt;};

	# Uncomment for debugging the watch response
	# open ($fh, &quot;&gt;&quot;, &quot;.git/watchman-response.json&quot;);
	# print $fh $response;
	# close $fh;

	die &quot;Watchman: command returned no output.\n&quot; .
	&quot;Falling back to scanning...\n&quot; if $response eq &quot;&quot;;
	die &quot;Watchman: command returned invalid output: $response\n&quot; .
	&quot;Falling back to scanning...\n&quot; unless $response =~ /^\{/;

	return $json_pkg-&gt;new-&gt;utf8-&gt;decode($response);
}

sub is_work_tree_watched {
	my ($output) = @_;
	my $error = $output-&gt;{error};
	if ($retry &gt; 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
		$retry--;
		my $response = qx/watchman watch &quot;$git_work_tree&quot;/;
		die &quot;Failed to make watchman watch '$git_work_tree'.\n&quot; .
		    &quot;Falling back to scanning...\n&quot; if $? != 0;
		$output = $json_pkg-&gt;new-&gt;utf8-&gt;decode($response);
		$error = $output-&gt;{error};
		die &quot;Watchman: $error.\n&quot; .
		&quot;Falling back to scanning...\n&quot; if $error;

		# Uncomment for debugging watchman output
		# open (my $fh, &quot;&gt;&quot;, &quot;.git/watchman-output.out&quot;);
		# close $fh;

		# Watchman will always return all files on the first query so
		# return the fast &quot;everything is dirty&quot; 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.
		my $o = watchman_clock();
		$error = $output-&gt;{error};

		die &quot;Watchman: $error.\n&quot; .
		&quot;Falling back to scanning...\n&quot; if $error;

		output_result($o-&gt;{clock}, (&quot;/&quot;));
		$last_update_token = $o-&gt;{clock};

		eval { launch_watchman() };
		return 0;
	}

	die &quot;Watchman: $error.\n&quot; .
	&quot;Falling back to scanning...\n&quot; if $error;

	return 1;
}

sub get_working_dir {
	my $working_dir;
	if ($^O =~ 'msys' || $^O =~ 'cygwin') {
		$working_dir = Win32::GetCwd();
		$working_dir =~ tr/\\/\//;
	} else {
		require Cwd;
		$working_dir = Cwd::cwd();
	}

	return $working_dir;
}
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