fsmonitor-watchman: fix variable reference and remove redundant code

The is_work_tree_watched() function in fsmonitor-watchman.sample has
two bugs:

1. Wrong variable in error check: After calling watchman_clock(), the
   result is stored in $o, but the code checks $output->{error} instead
   of $o->{error}. This means errors from the clock command are silently
   ignored.

2. Double output violates protocol: When the retry path triggers (the
   directory wasn't initially watched), output_result() is called with
   the "/" flag, then launch_watchman() is called recursively which
   calls output_result() again. This outputs two clock tokens to stdout,
   but git's fsmonitor v2 protocol expects exactly one response.

Fix #1 by checking $o->{error} after watchman_clock().

Fix #2 by removing the recursive launch_watchman() call. The "/"
"everything is dirty" flag already tells git to do a full scan, and
git will call the hook again on the next invocation with a valid clock
token.

With the recursive call removed, the $retry guard is no longer needed
since it only existed to prevent infinite recursion. Remove it.

Apply the same fixes to the test helper scripts in t/t7519/.

Signed-off-by: Paul Tarjan <github@paulisageek.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

3 files changed, 5 insertions, 21 deletions

diff --git a/t/t7519/fsmonitor-watchman b/t/t7519/fsmonitor-watchman
index 264b9daf83..bcc055c1e0 100755
--- a/t/t7519/fsmonitor-watchman
+++ b/t/t7519/fsmonitor-watchman
@@ -38,8 +38,6 @@ if ($^O =~ 'msys' || $^O =~ 'cygwin') {
 	$git_work_tree = Cwd::cwd();
 }
 
-my $retry = 1;
-
 launch_watchman();
 
 sub launch_watchman {
@@ -92,9 +90,8 @@ sub launch_watchman {
 
 	my $o = $json_pkg->new->utf8->decode($response);
 
-	if ($retry > 0 and $o->{error} and $o->{error} =~ m/unable to resolve root .* directory (.*) is not watched/) {
+	if ($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;
@@ -109,7 +106,6 @@ sub launch_watchman {
 		close $fh;
 
 		print "/\0";
-		eval { launch_watchman() };
 		exit 0;
 	}
 
diff --git a/t/t7519/fsmonitor-watchman-v2 b/t/t7519/fsmonitor-watchman-v2
index 14ed0aa42d..368604c278 100755
--- a/t/t7519/fsmonitor-watchman-v2
+++ b/t/t7519/fsmonitor-watchman-v2
@@ -29,8 +29,6 @@ if ($version ne 2) {
 
 my $git_work_tree = get_working_dir();
 
-my $retry = 1;
-
 my $json_pkg;
 eval {
 	require JSON::XS;
@@ -122,8 +120,7 @@ sub watchman_query {
 sub is_work_tree_watched {
 	my ($output) = @_;
 	my $error = $output->{error};
-	if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
-		$retry--;
+	if ($error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
 		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;
@@ -141,15 +138,12 @@ sub is_work_tree_watched {
 		# 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};
+		$error = $o->{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;
 	}
 
diff --git a/templates/hooks/fsmonitor-watchman.sample b/templates/hooks/fsmonitor-watchman.sample
index 23e856f5de..429e0a51c1 100755
--- a/templates/hooks/fsmonitor-watchman.sample
+++ b/templates/hooks/fsmonitor-watchman.sample
@@ -29,8 +29,6 @@ if ($version ne 2) {
 
 my $git_work_tree = get_working_dir();
 
-my $retry = 1;
-
 my $json_pkg;
 eval {
 	require JSON::XS;
@@ -123,8 +121,7 @@ sub watchman_query {
 sub is_work_tree_watched {
 	my ($output) = @_;
 	my $error = $output->{error};
-	if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
-		$retry--;
+	if ($error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
 		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;
@@ -142,15 +139,12 @@ sub is_work_tree_watched {
 		# 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};
+		$error = $o->{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;
 	}