#!/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 “query-watchman” and set
# ‘git config core.fsmonitor .git/hooks/query-watchman’
#
my ($version, $last_update_token) = @ARGV;
# Uncomment for debugging
# print STDERR “$0 $version $last_update_token\n”;
# Check the hook interface version
if ($version ne 2) {
die “Unsupported query-fsmonitor hook version ‘$version’.\n” .
“Falling back to scanning…\n”;
}
my $git_work_tree = get_working_dir();
my $retry = 1;
my $json_pkg;
eval {
require JSON::XS;
$json_pkg = “JSON::XS”;
1;
} or do {
require JSON::PP;
$json_pkg = “JSON::PP”;
};
launch_watchman();
sub launch_watchman {
my $o = watchman_query();
if (is_work_tree_watched($o)) {
output_result($o->{clock}, @{$o->{files}});
}
}
sub output_result {
my ($clockid, @files) = @_;
# Uncomment for debugging watchman output
# open (my $fh, “>”, “.git/watchman-output.out”);
# binmode $fh, “:utf8”;
# print $fh “$clockid\n@files\n”;
# close $fh;
binmode STDOUT, “:utf8”;
print $clockid;
print “\0”;
local $, = “\0”;
print @files;
}
sub watchman_clock {
my $response = qx/watchman clock “$git_work_tree”/;
die “Failed to get clock id on ‘$git_work_tree’.\n” .
“Falling back to scanning…\n” if $? != 0;
return $json_pkg->new->utf8->decode($response);
}
sub watchman_query {
my $pid = open2(\*CHLD_OUT, \*CHLD_IN, ‘watchman -j –no-pretty’)
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 $last_update_token but not from the .git folder.
#
# To accomplish this, we’re using the “since” generator to use the
# recency index to select candidate nodes and “fields” to limit the
# output to file names only. Then we’re using the “expression” term to
# further constrain the results.
if (substr($last_update_token, 0, 1) eq “c”) {
$last_update_token = “\”$last_update_token\””;
}
my $query = <<" END";
["query", "$git_work_tree", {
"since": $last_update_token,
"fields": ["name"],
"expression": ["not", ["dirname", ".git"]]
}]
END
# Uncomment for debugging the watchman query
# open (my $fh, ">“, “.git/watchman-query.json”);
# print $fh $query;
# close $fh;
print CHLD_IN $query;
close CHLD_IN;
my $response = do {local $/;
# Uncomment for debugging the watch response
# open ($fh, “>”, “.git/watchman-response.json”);
# print $fh $response;
# close $fh;
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 =~ /^\{/;
return $json_pkg->new->utf8->decode($response);
}
sub is_work_tree_watched {
my ($output) = @_;
my $error = $output->{error};
if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
$retry–;
my $response = qx/watchman watch “$git_work_tree”/;
die “Failed to make watchman watch ‘$git_work_tree’.\n” .
“Falling back to scanning…\n” if $? != 0;
$output = $json_pkg->new->utf8->decode($response);
$error = $output->{error};
die “Watchman: $error.\n” .
“Falling back to scanning…\n” if $error;
# Uncomment for debugging watchman output
# open (my $fh, “>”, “.git/watchman-output.out”);
# close $fh;
# 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.
my $o = watchman_clock();
$error = $output->{error};
die “Watchman: $error.\n” .
“Falling back to scanning…\n” if $error;
output_result($o->{clock}, (“/”));
$last_update_token = $o->{clock};
eval { launch_watchman() };
return 0;
}
die “Watchman: $error.\n” .
“Falling back to scanning…\n” 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;
}