1#!/usr/bin/perl
2
3use strict;
4use warnings;
5use IPC::Open2;
6
7# An example hook script to integrate Watchman
8# (https://facebook.github.io/watchman/) with git to speed up detecting
9# new and modified files.
10#
11# The hook is passed a version (currently 1) and a time in nanoseconds
12# formatted as a string and outputs to stdout all files that have been
13# modified since the given time. Paths must be relative to the root of
14# the working tree and separated by a single NUL.
15#
16# To enable this hook, rename this file to "query-watchman" and set
17# 'git config core.fsmonitor .git/hooks/query-watchman'
18#
19my ($version, $time) = @ARGV;
20
21# Check the hook interface version
22
23if ($version == 1) {
24	# convert nanoseconds to seconds
25	# subtract one second to make sure watchman will return all changes
26	$time = int ($time / 1000000000) - 1;
27} else {
28	die "Unsupported query-fsmonitor hook version '$version'.\n" .
29	    "Falling back to scanning...\n";
30}
31
32my $git_work_tree;
33if ($^O =~ 'msys' || $^O =~ 'cygwin') {
34	$git_work_tree = Win32::GetCwd();
35	$git_work_tree =~ tr/\\/\//;
36} else {
37	require Cwd;
38	$git_work_tree = Cwd::cwd();
39}
40
41my $retry = 1;
42
43launch_watchman();
44
45sub launch_watchman {
46
47	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
48	    or die "open2() failed: $!\n" .
49	    "Falling back to scanning...\n";
50
51	# In the query expression below we're asking for names of files that
52	# changed since $time but were not transient (ie created after
53	# $time but no longer exist).
54	#
55	# To accomplish this, we're using the "since" generator to use the
56	# recency index to select candidate nodes and "fields" to limit the
57	# output to file names only.
58
59	my $query = <<"	END";
60		["query", "$git_work_tree", {
61			"since": $time,
62			"fields": ["name"]
63		}]
64	END
65
66	print CHLD_IN $query;
67	close CHLD_IN;
68	my $response = do {local $/; <CHLD_OUT>};
69
70	die "Watchman: command returned no output.\n" .
71	    "Falling back to scanning...\n" if $response eq "";
72	die "Watchman: command returned invalid output: $response\n" .
73	    "Falling back to scanning...\n" unless $response =~ /^\{/;
74
75	my $json_pkg;
76	eval {
77		require JSON::XS;
78		$json_pkg = "JSON::XS";
79		1;
80	} or do {
81		require JSON::PP;
82		$json_pkg = "JSON::PP";
83	};
84
85	my $o = $json_pkg->new->utf8->decode($response);
86
87	if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
88		print STDERR "Adding '$git_work_tree' to watchman's watch list.\n";
89		$retry--;
90		qx/watchman watch "$git_work_tree"/;
91		die "Failed to make watchman watch '$git_work_tree'.\n" .
92		    "Falling back to scanning...\n" if $? != 0;
93
94		# Watchman will always return all files on the first query so
95		# return the fast "everything is dirty" flag to git and do the
96		# Watchman query just to get it over with now so we won't pay
97		# the cost in git to look up each individual file.
98		print "/\0";
99		eval { launch_watchman() };
100		exit 0;
101	}
102
103	die "Watchman: $o->{error}.\n" .
104	    "Falling back to scanning...\n" if $o->{error};
105
106	binmode STDOUT, ":utf8";
107	local $, = "\0";
108	print @{$o->{files}};
109}
110