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 2) and last update token
12# formatted as a string and outputs to stdout a new update token and
13# all files that have been modified since the update token. Paths must
14# be relative to the root of 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, $last_update_token) = @ARGV;
20
21# Uncomment for debugging
22# print STDERR "$0 $version $last_update_token\n";
23
24# Check the hook interface version
25if ($version ne 2) {
26	die "Unsupported query-fsmonitor hook version '$version'.\n" .
27	    "Falling back to scanning...\n";
28}
29
30my $git_work_tree = get_working_dir();
31
32my $retry = 1;
33
34my $json_pkg;
35eval {
36	require JSON::XS;
37	$json_pkg = "JSON::XS";
38	1;
39} or do {
40	require JSON::PP;
41	$json_pkg = "JSON::PP";
42};
43
44launch_watchman();
45
46sub launch_watchman {
47	my $o = watchman_query();
48	if (is_work_tree_watched($o)) {
49		output_result($o->{clock}, @{$o->{files}});
50	}
51}
52
53sub output_result {
54	my ($clockid, @files) = @_;
55
56	# Uncomment for debugging watchman output
57	# open (my $fh, ">", ".git/watchman-output.out");
58	# binmode $fh, ":utf8";
59	# print $fh "$clockid\n@files\n";
60	# close $fh;
61
62	binmode STDOUT, ":utf8";
63	print $clockid;
64	print "\0";
65	local $, = "\0";
66	print @files;
67}
68
69sub watchman_clock {
70	my $response = qx/watchman clock "$git_work_tree"/;
71	die "Failed to get clock id on '$git_work_tree'.\n" .
72		"Falling back to scanning...\n" if $? != 0;
73
74	return $json_pkg->new->utf8->decode($response);
75}
76
77sub watchman_query {
78	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
79	or die "open2() failed: $!\n" .
80	"Falling back to scanning...\n";
81
82	# In the query expression below we're asking for names of files that
83	# changed since $last_update_token but not from the .git folder.
84	#
85	# To accomplish this, we're using the "since" generator to use the
86	# recency index to select candidate nodes and "fields" to limit the
87	# output to file names only. Then we're using the "expression" term to
88	# further constrain the results.
89	my $last_update_line = "";
90	if (substr($last_update_token, 0, 1) eq "c") {
91		$last_update_token = "\"$last_update_token\"";
92		$last_update_line = qq[\n"since": $last_update_token,];
93	}
94	my $query = <<"	END";
95		["query", "$git_work_tree", {$last_update_line
96			"fields": ["name"],
97			"expression": ["not", ["dirname", ".git"]]
98		}]
99	END
100
101	# Uncomment for debugging the watchman query
102	# open (my $fh, ">", ".git/watchman-query.json");
103	# print $fh $query;
104	# close $fh;
105
106	print CHLD_IN $query;
107	close CHLD_IN;
108	my $response = do {local $/; <CHLD_OUT>};
109
110	# Uncomment for debugging the watch response
111	# open ($fh, ">", ".git/watchman-response.json");
112	# print $fh $response;
113	# close $fh;
114
115	die "Watchman: command returned no output.\n" .
116	"Falling back to scanning...\n" if $response eq "";
117	die "Watchman: command returned invalid output: $response\n" .
118	"Falling back to scanning...\n" unless $response =~ /^\{/;
119
120	return $json_pkg->new->utf8->decode($response);
121}
122
123sub is_work_tree_watched {
124	my ($output) = @_;
125	my $error = $output->{error};
126	if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
127		$retry--;
128		my $response = qx/watchman watch "$git_work_tree"/;
129		die "Failed to make watchman watch '$git_work_tree'.\n" .
130		    "Falling back to scanning...\n" if $? != 0;
131		$output = $json_pkg->new->utf8->decode($response);
132		$error = $output->{error};
133		die "Watchman: $error.\n" .
134		"Falling back to scanning...\n" if $error;
135
136		# Uncomment for debugging watchman output
137		# open (my $fh, ">", ".git/watchman-output.out");
138		# close $fh;
139
140		# Watchman will always return all files on the first query so
141		# return the fast "everything is dirty" flag to git and do the
142		# Watchman query just to get it over with now so we won't pay
143		# the cost in git to look up each individual file.
144		my $o = watchman_clock();
145		$error = $output->{error};
146
147		die "Watchman: $error.\n" .
148		"Falling back to scanning...\n" if $error;
149
150		output_result($o->{clock}, ("/"));
151		$last_update_token = $o->{clock};
152
153		eval { launch_watchman() };
154		return 0;
155	}
156
157	die "Watchman: $error.\n" .
158	"Falling back to scanning...\n" if $error;
159
160	return 1;
161}
162
163sub get_working_dir {
164	my $working_dir;
165	if ($^O =~ 'msys' || $^O =~ 'cygwin') {
166		$working_dir = Win32::GetCwd();
167		$working_dir =~ tr/\\/\//;
168	} else {
169		require Cwd;
170		$working_dir = Cwd::cwd();
171	}
172
173	return $working_dir;
174}
175