fsmonitor: enhance existing comments

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 30 insertions, 7 deletions

diff --git a/fsmonitor.c b/fsmonitor.c
index ab9bfc60b3..ec4c46407c 100644
--- a/fsmonitor.c
+++ b/fsmonitor.c
@@ -301,9 +301,25 @@ void refresh_fsmonitor(struct index_state *istate)
 			core_fsmonitor, query_success ? "success" : "failure");
 	}
 
-	/* a fsmonitor process can return '/' to indicate all entries are invalid */
+	/*
+	 * The response from FSMonitor (excluding the header token) is
+	 * either:
+	 *
+	 * [a] a (possibly empty) list of NUL delimited relative
+	 *     pathnames of changed paths.  This list can contain
+	 *     files and directories.  Directories have a trailing
+	 *     slash.
+	 *
+	 * [b] a single '/' to indicate the provider had no
+	 *     information and that we should consider everything
+	 *     invalid.  We call this a trivial response.
+	 */
 	if (query_success && query_result.buf[bol] != '/') {
-		/* Mark all entries returned by the monitor as dirty */
+		/*
+		 * Mark all pathnames returned by the monitor as dirty.
+		 *
+		 * This updates both the cache-entries and the untracked-cache.
+		 */
 		buf = query_result.buf;
 		for (i = bol; i < query_result.len; i++) {
 			if (buf[i] != '\0')
@@ -318,11 +334,15 @@ void refresh_fsmonitor(struct index_state *istate)
 		if (istate->untracked)
 			istate->untracked->use_fsmonitor = 1;
 	} else {
-
-		/* We only want to run the post index changed hook if we've actually changed entries, so keep track
-		 * if we actually changed entries or not */
+		/*
+		 * We received a trivial response, so invalidate everything.
+		 *
+		 * We only want to run the post index changed hook if
+		 * we've actually changed entries, so keep track if we
+		 * actually changed entries or not.
+		 */
 		int is_cache_changed = 0;
-		/* Mark all entries invalid */
+
 		for (i = 0; i < istate->cache_nr; i++) {
 			if (istate->cache[i]->ce_flags & CE_FSMONITOR_VALID) {
 				is_cache_changed = 1;
@@ -330,7 +350,10 @@ void refresh_fsmonitor(struct index_state *istate)
 			}
 		}
 
-		/* If we're going to check every file, ensure we save the results */
+		/*
+		 * If we're going to check every file, ensure we save
+		 * the results.
+		 */
 		if (is_cache_changed)
 			istate->cache_changed |= FSMONITOR_CHANGED;