templates/hooks--fsmonitor-watchman.sample

   1 #!/usr/bin/perl
   2
   3 use strict;
   4 use warnings;
   5 use 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 #
  19 my ($version, $time) = @ARGV;
  20
  21 # Check the hook interface version
  22
  23 if ($version == 1) {
  24         # convert nanoseconds to seconds
  25         $time = int $time / 1000000000;
  26 } else {
  27         die "Unsupported query-fsmonitor hook version '$version'.\n" .
  28             "Falling back to scanning...\n";
  29 }
  30
  31 my $git_work_tree;
  32 if ($^O =~ 'msys' || $^O =~ 'cygwin') {
  33         $git_work_tree = Win32::GetCwd();
  34         $git_work_tree =~ tr/\\/\//;
  35 } else {
  36         require Cwd;
  37         $git_work_tree = Cwd::cwd();
  38 }
  39
  40 my $retry = 1;
  41
  42 launch_watchman();
  43
  44 sub launch_watchman {
  45
  46         my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
  47             or die "open2() failed: $!\n" .
  48             "Falling back to scanning...\n";
  49
  50         # In the query expression below we're asking for names of files that
  51         # changed since $time but were not transient (ie created after
  52         # $time but no longer exist).
  53         #
  54         # To accomplish this, we're using the "since" generator to use the
  55         # recency index to select candidate nodes and "fields" to limit the
  56         # output to file names only. Then we're using the "expression" term to
  57         # further constrain the results.
  58         #
  59         # The category of transient files that we want to ignore will have a
  60         # creation clock (cclock) newer than $time_t value and will also not
  61         # currently exist.
  62
  63         my $query = <<" END";
  64                 ["query", "$git_work_tree", {
  65                         "since": $time,
  66                         "fields": ["name"],
  67                         "expression": ["not", ["allof", ["since", $time, "cclock"], ["not", "exists"]]]
  68                 }]
  69         END
  70
  71         print CHLD_IN $query;
  72         close CHLD_IN;
  73         my $response = do {local $/; <CHLD_OUT>};
  74
  75         die "Watchman: command returned no output.\n" .
  76             "Falling back to scanning...\n" if $response eq "";
  77         die "Watchman: command returned invalid output: $response\n" .
  78             "Falling back to scanning...\n" unless $response =~ /^\{/;
  79
  80         my $json_pkg;
  81         eval {
  82                 require JSON::XS;
  83                 $json_pkg = "JSON::XS";
  84                 1;
  85         } or do {
  86                 require JSON::PP;
  87                 $json_pkg = "JSON::PP";
  88         };
  89
  90         my $o = $json_pkg->new->utf8->decode($response);
  91
  92         if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
  93                 print STDERR "Adding '$git_work_tree' to watchman's watch list.\n";
  94                 $retry--;
  95                 qx/watchman watch "$git_work_tree"/;
  96                 die "Failed to make watchman watch '$git_work_tree'.\n" .
  97                     "Falling back to scanning...\n" if $? != 0;
  98
  99                 # Watchman will always return all files on the first query so
 100                 # return the fast "everything is dirty" flag to git and do the
 101                 # Watchman query just to get it over with now so we won't pay
 102                 # the cost in git to look up each individual file.
 103                 print "/\0";
 104                 eval { launch_watchman() };
 105                 exit 0;
 106         }
 107
 108         die "Watchman: $o->{error}.\n" .
 109             "Falling back to scanning...\n" if $o->{error};
 110
 111         binmode STDOUT, ":utf8";
 112         local $, = "\0";
 113         print @{$o->{files}};
 114 }