Adding upstream version 1:2.39.2.upstream/1%2.39.2upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

7 files changed, 870 insertions, 0 deletions

diff --git a/t/t7519-status-fsmonitor.sh b/t/t7519-status-fsmonitor.sh
new file mode 100755
index 0000000..8348e3a
--- /dev/null
+++ b/t/t7519-status-fsmonitor.sh
@@ -0,0 +1,480 @@
+#!/bin/sh
+
+test_description='git status with file system watcher'
+
+. ./test-lib.sh
+
+# Note, after "git reset --hard HEAD" no extensions exist other than 'TREE'
+# "git update-index --fsmonitor" can be used to get the extension written
+# before testing the results.
+
+clean_repo () {
+	git reset --hard HEAD &&
+	git clean -fd
+}
+
+dirty_repo () {
+	: >untracked &&
+	: >dir1/untracked &&
+	: >dir2/untracked &&
+	echo 1 >modified &&
+	echo 2 >dir1/modified &&
+	echo 3 >dir2/modified &&
+	echo 4 >new &&
+	echo 5 >dir1/new &&
+	echo 6 >dir2/new
+}
+
+write_integration_script () {
+	test_hook --setup --clobber fsmonitor-test<<-\EOF
+	if test "$#" -ne 2
+	then
+		echo "$0: exactly 2 arguments expected"
+		exit 2
+	fi
+	if test "$1" != 2
+	then
+		echo "Unsupported core.fsmonitor hook version." >&2
+		exit 1
+	fi
+	printf "last_update_token\0"
+	printf "untracked\0"
+	printf "dir1/untracked\0"
+	printf "dir2/untracked\0"
+	printf "modified\0"
+	printf "dir1/modified\0"
+	printf "dir2/modified\0"
+	printf "new\0"
+	printf "dir1/new\0"
+	printf "dir2/new\0"
+	EOF
+}
+
+test_lazy_prereq UNTRACKED_CACHE '
+	{ git update-index --test-untracked-cache; ret=$?; } &&
+	test $ret -ne 1
+'
+
+# Test that we detect and disallow repos that are incompatible with FSMonitor.
+test_expect_success 'incompatible bare repo' '
+	test_when_finished "rm -rf ./bare-clone actual expect" &&
+	git init --bare bare-clone &&
+
+	test_must_fail \
+		git -C ./bare-clone -c core.fsmonitor=foo \
+			update-index --fsmonitor 2>actual &&
+	grep "bare repository .* is incompatible with fsmonitor" actual &&
+
+	test_must_fail \
+		git -C ./bare-clone -c core.fsmonitor=true \
+			update-index --fsmonitor 2>actual &&
+	grep "bare repository .* is incompatible with fsmonitor" actual
+'
+
+test_expect_success FSMONITOR_DAEMON 'run fsmonitor-daemon in bare repo' '
+	test_when_finished "rm -rf ./bare-clone actual" &&
+	git init --bare bare-clone &&
+	test_must_fail git -C ./bare-clone fsmonitor--daemon run 2>actual &&
+	grep "bare repository .* is incompatible with fsmonitor" actual
+'
+
+test_expect_success MINGW,FSMONITOR_DAEMON 'run fsmonitor-daemon in virtual repo' '
+	test_when_finished "rm -rf ./fake-virtual-clone actual" &&
+	git init fake-virtual-clone &&
+	test_must_fail git -C ./fake-virtual-clone \
+			   -c core.virtualfilesystem=true \
+			   fsmonitor--daemon run 2>actual &&
+	grep "virtual repository .* is incompatible with fsmonitor" actual
+'
+
+test_expect_success 'setup' '
+	: >tracked &&
+	: >modified &&
+	mkdir dir1 &&
+	: >dir1/tracked &&
+	: >dir1/modified &&
+	mkdir dir2 &&
+	: >dir2/tracked &&
+	: >dir2/modified &&
+	git -c core.fsmonitor= add . &&
+	git -c core.fsmonitor= commit -m initial &&
+	git config core.fsmonitor .git/hooks/fsmonitor-test &&
+	cat >.gitignore <<-\EOF
+	.gitignore
+	expect*
+	actual*
+	marker*
+	trace2*
+	EOF
+'
+
+# test that the fsmonitor extension is off by default
+test_expect_success 'fsmonitor extension is off by default' '
+	test-tool dump-fsmonitor >actual &&
+	grep "^no fsmonitor" actual
+'
+
+# test that "update-index --fsmonitor" adds the fsmonitor extension
+test_expect_success 'update-index --fsmonitor" adds the fsmonitor extension' '
+	git update-index --fsmonitor &&
+	test-tool dump-fsmonitor >actual &&
+	grep "^fsmonitor last update" actual
+'
+
+# test that "update-index --no-fsmonitor" removes the fsmonitor extension
+test_expect_success 'update-index --no-fsmonitor" removes the fsmonitor extension' '
+	git update-index --no-fsmonitor &&
+	test-tool dump-fsmonitor >actual &&
+	grep "^no fsmonitor" actual
+'
+
+cat >expect <<EOF &&
+h dir1/modified
+H dir1/tracked
+h dir2/modified
+H dir2/tracked
+h modified
+H tracked
+EOF
+
+# test that "update-index --fsmonitor-valid" sets the fsmonitor valid bit
+test_expect_success 'update-index --fsmonitor-valid" sets the fsmonitor valid bit' '
+	test_hook fsmonitor-test<<-\EOF &&
+		printf "last_update_token\0"
+	EOF
+	git update-index --fsmonitor &&
+	git update-index --fsmonitor-valid dir1/modified &&
+	git update-index --fsmonitor-valid dir2/modified &&
+	git update-index --fsmonitor-valid modified &&
+	git ls-files -f >actual &&
+	test_cmp expect actual
+'
+
+cat >expect <<EOF &&
+H dir1/modified
+H dir1/tracked
+H dir2/modified
+H dir2/tracked
+H modified
+H tracked
+EOF
+
+# test that "update-index --no-fsmonitor-valid" clears the fsmonitor valid bit
+test_expect_success 'update-index --no-fsmonitor-valid" clears the fsmonitor valid bit' '
+	git update-index --no-fsmonitor-valid dir1/modified &&
+	git update-index --no-fsmonitor-valid dir2/modified &&
+	git update-index --no-fsmonitor-valid modified &&
+	git ls-files -f >actual &&
+	test_cmp expect actual
+'
+
+cat >expect <<EOF &&
+H dir1/modified
+H dir1/tracked
+H dir2/modified
+H dir2/tracked
+H modified
+H tracked
+EOF
+
+# test that all files returned by the script get flagged as invalid
+test_expect_success 'all files returned by integration script get flagged as invalid' '
+	write_integration_script &&
+	dirty_repo &&
+	git update-index --fsmonitor &&
+	git ls-files -f >actual &&
+	test_cmp expect actual
+'
+
+cat >expect <<EOF &&
+H dir1/modified
+h dir1/new
+H dir1/tracked
+H dir2/modified
+h dir2/new
+H dir2/tracked
+H modified
+h new
+H tracked
+EOF
+
+# test that newly added files are marked valid
+test_expect_success 'newly added files are marked valid' '
+	test_hook --setup --clobber fsmonitor-test<<-\EOF &&
+		printf "last_update_token\0"
+	EOF
+	git add new &&
+	git add dir1/new &&
+	git add dir2/new &&
+	git ls-files -f >actual &&
+	test_cmp expect actual
+'
+
+cat >expect <<EOF &&
+H dir1/modified
+h dir1/new
+h dir1/tracked
+H dir2/modified
+h dir2/new
+h dir2/tracked
+H modified
+h new
+h tracked
+EOF
+
+# test that all unmodified files get marked valid
+test_expect_success 'all unmodified files get marked valid' '
+	# modified files result in update-index returning 1
+	test_must_fail git update-index --refresh --force-write-index &&
+	git ls-files -f >actual &&
+	test_cmp expect actual
+'
+
+cat >expect <<EOF &&
+H dir1/modified
+h dir1/tracked
+h dir2/modified
+h dir2/tracked
+h modified
+h tracked
+EOF
+
+# test that *only* files returned by the integration script get flagged as invalid
+test_expect_success '*only* files returned by the integration script get flagged as invalid' '
+	test_hook --clobber fsmonitor-test<<-\EOF &&
+	printf "last_update_token\0"
+	printf "dir1/modified\0"
+	EOF
+	clean_repo &&
+	git update-index --refresh --force-write-index &&
+	echo 1 >modified &&
+	echo 2 >dir1/modified &&
+	echo 3 >dir2/modified &&
+	test_must_fail git update-index --refresh --force-write-index &&
+	git ls-files -f >actual &&
+	test_cmp expect actual
+'
+
+# Ensure commands that call refresh_index() to move the index back in time
+# properly invalidate the fsmonitor cache
+test_expect_success 'refresh_index() invalidates fsmonitor cache' '
+	clean_repo &&
+	dirty_repo &&
+	write_integration_script &&
+	git add . &&
+	test_hook --clobber fsmonitor-test<<-\EOF &&
+	EOF
+	git commit -m "to reset" &&
+	git reset HEAD~1 &&
+	git status >actual &&
+	git -c core.fsmonitor= status >expect &&
+	test_cmp expect actual
+'
+
+# test fsmonitor with and without preloadIndex
+preload_values="false true"
+for preload_val in $preload_values
+do
+	test_expect_success "setup preloadIndex to $preload_val" '
+		git config core.preloadIndex $preload_val &&
+		if test $preload_val = true
+		then
+			GIT_TEST_PRELOAD_INDEX=$preload_val && export GIT_TEST_PRELOAD_INDEX
+		else
+			sane_unset GIT_TEST_PRELOAD_INDEX
+		fi
+	'
+
+	# test fsmonitor with and without the untracked cache (if available)
+	uc_values="false"
+	test_have_prereq UNTRACKED_CACHE && uc_values="false true"
+	for uc_val in $uc_values
+	do
+		test_expect_success "setup untracked cache to $uc_val" '
+			git config core.untrackedcache $uc_val
+		'
+
+		# Status is well tested elsewhere so we'll just ensure that the results are
+		# the same when using core.fsmonitor.
+		test_expect_success 'compare status with and without fsmonitor' '
+			write_integration_script &&
+			clean_repo &&
+			dirty_repo &&
+			git add new &&
+			git add dir1/new &&
+			git add dir2/new &&
+			git status >actual &&
+			git -c core.fsmonitor= status >expect &&
+			test_cmp expect actual
+		'
+
+		# Make sure it's actually skipping the check for modified and untracked
+		# (if enabled) files unless it is told about them.
+		test_expect_success "status doesn't detect unreported modifications" '
+			test_hook --clobber fsmonitor-test<<-\EOF &&
+			printf "last_update_token\0"
+			:>marker
+			EOF
+			clean_repo &&
+			git status &&
+			test_path_is_file marker &&
+			dirty_repo &&
+			rm -f marker &&
+			git status >actual &&
+			test_path_is_file marker &&
+			test_i18ngrep ! "Changes not staged for commit:" actual &&
+			if test $uc_val = true
+			then
+				test_i18ngrep ! "Untracked files:" actual
+			fi &&
+			if test $uc_val = false
+			then
+				test_i18ngrep "Untracked files:" actual
+			fi &&
+			rm -f marker
+		'
+	done
+done
+
+# test that splitting the index doesn't interfere
+test_expect_success 'splitting the index results in the same state' '
+	write_integration_script &&
+	dirty_repo &&
+	git update-index --fsmonitor  &&
+	git ls-files -f >expect &&
+	test-tool dump-fsmonitor >&2 && echo &&
+	git update-index --fsmonitor --split-index &&
+	test-tool dump-fsmonitor >&2 && echo &&
+	git ls-files -f >actual &&
+	test_cmp expect actual
+'
+
+test_expect_success UNTRACKED_CACHE 'ignore .git changes when invalidating UNTR' '
+	test_create_repo dot-git &&
+	(
+		cd dot-git &&
+		: >tracked &&
+		test-tool chmtime =-60 tracked &&
+		: >modified &&
+		test-tool chmtime =-60 modified &&
+		mkdir dir1 &&
+		: >dir1/tracked &&
+		test-tool chmtime =-60 dir1/tracked &&
+		: >dir1/modified &&
+		test-tool chmtime =-60 dir1/modified &&
+		mkdir dir2 &&
+		: >dir2/tracked &&
+		test-tool chmtime =-60 dir2/tracked &&
+		: >dir2/modified &&
+		test-tool chmtime =-60 dir2/modified &&
+		write_integration_script &&
+		git config core.fsmonitor .git/hooks/fsmonitor-test &&
+		git update-index --untracked-cache &&
+		git update-index --fsmonitor &&
+		git status &&
+		GIT_TRACE2_PERF="$TRASH_DIRECTORY/trace-before" \
+		git status &&
+		test-tool dump-untracked-cache >../before
+	) &&
+	cat >>dot-git/.git/hooks/fsmonitor-test <<-\EOF &&
+	printf ".git\0"
+	printf ".git/index\0"
+	printf "dir1/.git\0"
+	printf "dir1/.git/index\0"
+	EOF
+	(
+		cd dot-git &&
+		GIT_TRACE2_PERF="$TRASH_DIRECTORY/trace-after" \
+		git status &&
+		test-tool dump-untracked-cache >../after
+	) &&
+	grep "directory-invalidation" trace-before | cut -d"|" -f 9 >>before &&
+	grep "directory-invalidation" trace-after  | cut -d"|" -f 9 >>after &&
+	# UNTR extension unchanged, dir invalidation count unchanged
+	test_cmp before after
+'
+
+test_expect_success 'discard_index() also discards fsmonitor info' '
+	test_config core.fsmonitor "$TEST_DIRECTORY/t7519/fsmonitor-all" &&
+	test_might_fail git update-index --refresh &&
+	test-tool read-cache --print-and-refresh=tracked 2 >actual &&
+	printf "tracked is%s up to date\n" "" " not" >expect &&
+	test_cmp expect actual
+'
+
+# Test unstaging entries that:
+#  - Are not flagged with CE_FSMONITOR_VALID
+#  - Have a position in the index >= the number of entries present in the index
+#    after unstaging.
+test_expect_success 'status succeeds after staging/unstaging' '
+	test_create_repo fsmonitor-stage-unstage &&
+	(
+		cd fsmonitor-stage-unstage &&
+		test_commit initial &&
+		git update-index --fsmonitor &&
+		removed=$(test_seq 1 100 | sed "s/^/z/") &&
+		touch $removed &&
+		git add $removed &&
+		git config core.fsmonitor "$TEST_DIRECTORY/t7519/fsmonitor-env" &&
+		FSMONITOR_LIST="$removed" git restore -S $removed &&
+		FSMONITOR_LIST="$removed" git status
+	)
+'
+
+# Usage:
+# check_sparse_index_behavior [!]
+# If "!" is supplied, then we verify that we do not call ensure_full_index
+# during a call to 'git status'. Otherwise, we verify that we _do_ call it.
+check_sparse_index_behavior () {
+	git -C full status --porcelain=v2 >expect &&
+	GIT_TRACE2_EVENT="$(pwd)/trace2.txt" \
+		git -C sparse status --porcelain=v2 >actual &&
+	test_region $1 index ensure_full_index trace2.txt &&
+	test_region fsm_hook query trace2.txt &&
+	test_cmp expect actual &&
+	rm trace2.txt
+}
+
+test_expect_success 'status succeeds with sparse index' '
+	(
+		sane_unset GIT_TEST_SPLIT_INDEX &&
+
+		git clone . full &&
+		git clone --sparse . sparse &&
+		git -C sparse sparse-checkout init --cone --sparse-index &&
+		git -C sparse sparse-checkout set dir1 dir2 &&
+
+		test_hook --clobber fsmonitor-test <<-\EOF &&
+			printf "last_update_token\0"
+		EOF
+		git -C full config core.fsmonitor ../.git/hooks/fsmonitor-test &&
+		git -C sparse config core.fsmonitor ../.git/hooks/fsmonitor-test &&
+		check_sparse_index_behavior ! &&
+
+		test_hook --clobber fsmonitor-test <<-\EOF &&
+			printf "last_update_token\0"
+			printf "dir1/modified\0"
+		EOF
+		check_sparse_index_behavior ! &&
+
+		git -C sparse sparse-checkout add dir1a &&
+
+		for repo in full sparse
+		do
+			cp -r $repo/dir1 $repo/dir1a &&
+			git -C $repo add dir1a &&
+			git -C $repo commit -m "add dir1a" || return 1
+		done &&
+		git -C sparse sparse-checkout set dir1 dir2 &&
+
+		# This one modifies outside the sparse-checkout definition
+		# and hence we expect to expand the sparse-index.
+		test_hook --clobber fsmonitor-test <<-\EOF &&
+			printf "last_update_token\0"
+			printf "dir1a/modified\0"
+		EOF
+		check_sparse_index_behavior
+	)
+'
+
+test_done
diff --git a/t/t7519/fsmonitor-all b/t/t7519/fsmonitor-all
new file mode 100755
index 0000000..94ab66b
--- /dev/null
+++ b/t/t7519/fsmonitor-all
@@ -0,0 +1,23 @@
+#!/bin/sh
+#
+# An test hook script to integrate with git to test fsmonitor.
+#
+# The hook is passed a version (currently 1) and a time in nanoseconds
+# formatted as a string and outputs to stdout all files that have been
+# modified since the given time. Paths must be relative to the root of
+# the working tree and separated by a single NUL.
+#
+#echo "$0 $*" >&2
+
+if test "$#" -ne 2
+then
+	echo "$0: exactly 2 arguments expected" >&2
+	exit 2
+fi
+
+if test "$1" != 1
+then
+	exit 1
+fi
+
+echo "/"
diff --git a/t/t7519/fsmonitor-all-v2 b/t/t7519/fsmonitor-all-v2
new file mode 100755
index 0000000..061907e
--- /dev/null
+++ b/t/t7519/fsmonitor-all-v2
@@ -0,0 +1,21 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+#
+# An test hook script to integrate with git to test fsmonitor.
+#
+# The hook is passed a version (currently 2) and since token
+# formatted as a string and outputs to stdout all files that have been
+# modified since the given time. Paths must be relative to the root of
+# the working tree and separated by a single NUL.
+#
+#echo "$0 $*" >&2
+my ($version, $last_update_token) = @ARGV;
+
+if ($version ne 2) {
+	print "Unsupported query-fsmonitor hook version '$version'.\n";
+	exit 1;
+}
+
+print "last_update_token\0/\0"
diff --git a/t/t7519/fsmonitor-env b/t/t7519/fsmonitor-env
new file mode 100755
index 0000000..8f1f7ab
--- /dev/null
+++ b/t/t7519/fsmonitor-env
@@ -0,0 +1,24 @@
+#!/bin/sh
+#
+# An test hook script to integrate with git to test fsmonitor.
+#
+# The hook is passed a version (currently 1) and a time in nanoseconds
+# formatted as a string and outputs to stdout all files that have been
+# modified since the given time. Paths must be relative to the root of
+# the working tree and separated by a single NUL.
+#
+#echo "$0 $*" >&2
+
+if test "$#" -ne 2
+then
+	echo "$0: exactly 2 arguments expected" >&2
+	exit 2
+fi
+
+if test "$1" != 1
+then
+	echo "Unsupported core.fsmonitor hook version." >&2
+	exit 1
+fi
+
+printf '%s\n' $FSMONITOR_LIST
diff --git a/t/t7519/fsmonitor-none b/t/t7519/fsmonitor-none
new file mode 100755
index 0000000..ed9cf5a
--- /dev/null
+++ b/t/t7519/fsmonitor-none
@@ -0,0 +1,22 @@
+#!/bin/sh
+#
+# An test hook script to integrate with git to test fsmonitor.
+#
+# The hook is passed a version (currently 1) and a time in nanoseconds
+# formatted as a string and outputs to stdout all files that have been
+# modified since the given time. Paths must be relative to the root of
+# the working tree and separated by a single NUL.
+#
+#echo "$0 $*" >&2
+
+if test "$#" -ne 2
+then
+	echo "$0: exactly 2 arguments expected" >&2
+	exit 2
+fi
+
+if test "$1" != 1
+then
+	echo "Unsupported core.fsmonitor hook version." >&2
+	exit 1
+fi
diff --git a/t/t7519/fsmonitor-watchman b/t/t7519/fsmonitor-watchman
new file mode 100755
index 0000000..264b9da
--- /dev/null
+++ b/t/t7519/fsmonitor-watchman
@@ -0,0 +1,127 @@
+#!/usr/bin/perl
+
+use strict;
+use warnings;
+use IPC::Open2;
+
+# An example hook script to integrate Watchman
+# (https://facebook.github.io/watchman/) with git to speed up detecting
+# new and modified files.
+#
+# The hook is passed a version (currently 1) and a time in nanoseconds
+# formatted as a string and outputs to stdout all files that have been
+# modified since the given time. Paths must be relative to the root of
+# the working tree and separated by a single NUL.
+#
+# To enable this hook, rename this file to "query-watchman" and set
+# 'git config core.fsmonitor .git/hooks/query-watchman'
+#
+my ($version, $time) = @ARGV;
+#print STDERR "$0 $version $time\n";
+
+# Check the hook interface version
+
+if ($version == 1) {
+	# convert nanoseconds to seconds
+	# subtract one second to make sure watchman will return all changes
+	$time = int ($time / 1000000000) - 1;
+} else {
+	exit 1;
+}
+
+my $git_work_tree;
+if ($^O =~ 'msys' || $^O =~ 'cygwin') {
+	$git_work_tree = Win32::GetCwd();
+	$git_work_tree =~ tr/\\/\//;
+} else {
+	require Cwd;
+	$git_work_tree = Cwd::cwd();
+}
+
+my $retry = 1;
+
+launch_watchman();
+
+sub launch_watchman {
+
+	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j')
+	    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 $time but were not transient (ie created after
+	# $time but no longer exist).
+	#
+	# 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.
+
+	my $query = <<"	END";
+		["query", "$git_work_tree", {
+			"since": $time,
+			"fields": ["name"]
+		}]
+	END
+	
+	open (my $fh, ">", ".git/watchman-query.json");
+	print $fh $query;
+	close $fh;
+
+	print CHLD_IN $query;
+	close CHLD_IN;
+	my $response = do {local $/; <CHLD_OUT>};
+
+	open ($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 =~ /^\{/;
+
+	my $json_pkg;
+	eval {
+		require JSON::XS;
+		$json_pkg = "JSON::XS";
+		1;
+	} or do {
+		require JSON::PP;
+		$json_pkg = "JSON::PP";
+	};
+
+	my $o = $json_pkg->new->utf8->decode($response);
+
+	if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
+		print STDERR "Adding '$git_work_tree' to watchman's watch list.\n";
+		$retry--;
+		qx/watchman watch "$git_work_tree"/;
+		die "Failed to make watchman watch '$git_work_tree'.\n" .
+		    "Falling back to scanning...\n" if $? != 0;
+
+		# Watchman will always return all files on the first query so
+		# return the fast "everything is dirty" flag to git and do the
+		# Watchman query just to get it over with now so we won't pay
+		# the cost in git to look up each individual file.
+
+		open ($fh, ">", ".git/watchman-output.out");
+		print "/\0";
+		close $fh;
+
+		print "/\0";
+		eval { launch_watchman() };
+		exit 0;
+	}
+
+	die "Watchman: $o->{error}.\n" .
+	    "Falling back to scanning...\n" if $o->{error};
+
+	open ($fh, ">", ".git/watchman-output.out");
+	binmode $fh, ":utf8";
+	print $fh @{$o->{files}};
+	close $fh;
+
+	binmode STDOUT, ":utf8";
+	local $, = "\0";
+	print @{$o->{files}};
+}
diff --git a/t/t7519/fsmonitor-watchman-v2 b/t/t7519/fsmonitor-watchman-v2
new file mode 100755
index 0000000..14ed0aa
--- /dev/null
+++ b/t/t7519/fsmonitor-watchman-v2
@@ -0,0 +1,173 @@
+#!/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 $/; <CHLD_OUT>};
+
+	# Uncomment for debugging the watch response
+	# open ($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;
+}