[PATCH] fsmonitor: query watchman with right valid json

[Son Luong Ngoc <sluongng@xxxxxxxxx>]

In rare circumstances where the current git index does not carry the
last_update_token, the fsmonitor v2 hook will be invoked with an
empty string which would caused the final rendered json to be invalid.

  ["query", "/path/to/my/git/repository/", {
          "since": ,
          "fields": ["name"],
          "expression": ["not", ["dirname", ".git"]]
  }]

Which will left user with the following error message

  > git status
  failed to parse command from stdin: line 2, column 13, position 67: unexpected token near ','
  Watchman: command returned no output.
  Falling back to scanning...

Hide the "since" field in json query when "last_update_token" is empty.

Signed-off-by: Son Luong Ngoc <sluongng@xxxxxxxxx>
---
 templates/hooks--fsmonitor-watchman.sample | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/templates/hooks--fsmonitor-watchman.sample b/templates/hooks--fsmonitor-watchman.sample
index 14ed0aa42d..b4ee86dfc4 100755
--- a/templates/hooks--fsmonitor-watchman.sample
+++ b/templates/hooks--fsmonitor-watchman.sample
@@ -79,6 +79,12 @@ sub watchman_query {
 	or die "open2() failed: $!\n" .
 	"Falling back to scanning...\n";
 
+	my $query = <<"	END";
+		["query", "$git_work_tree", {
+			"fields": ["name"],
+			"expression": ["not", ["dirname", ".git"]]
+		}]
+	END
 	# In the query expression below we're asking for names of files that
 	# changed since $last_update_token but not from the .git folder.
 	#
@@ -87,15 +93,14 @@ sub watchman_query {
 	# output to file names only. Then we're using the "expression" term to
 	# further constrain the results.
 	if (substr($last_update_token, 0, 1) eq "c") {
-		$last_update_token = "\"$last_update_token\"";
+		$query = <<"		END";
+			["query", "$git_work_tree", {
+				"since": "$last_update_token",
+				"fields": ["name"],
+				"expression": ["not", ["dirname", ".git"]]
+			}]
+		END
 	}
-	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");
-- 
2.36.1.231.g6924ef9a07