fsmonitor: remove custom loop from non-directory path handler

Refactor the code that handles refresh events for pathnames that do
not contain a trailing slash.  Instead of using a custom loop to try
to scan the index and detect if the FSEvent named a file or might be a
directory prefix, use the recently created helper function to do that.

Also update the comments to describe what and why we are doing this.

On platforms that DO NOT annotate FS events with a trailing
slash, if we fail to find an exact match for the pathname
in the index, we do not know if the pathname represents a
directory or simply an untracked file.  Pretend that the pathname
is a directory and try again before assuming it is an untracked
file.

Signed-off-by: Jeff Hostetler <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

fsmonitor.c

@@ -183,11 +183,23 @@ static int query_fsmonitor_hook(struct repository *r,
 	return result;
 }
 
+static size_t handle_path_with_trailing_slash(
+	struct index_state *istate, const char *name, int pos);
+
+/*
+ * The daemon sent an observed pathname without a trailing slash.
+ * (This is the normal case.)  We do not know if it is a tracked or
+ * untracked file, a sparse-directory, or a populated directory (on a
+ * platform such as Windows where FSEvents are not qualified).
+ *
+ * The pathname contains the observed case reported by the FS. We
+ * do not know it is case-correct or -incorrect.
+ *
+ * Assume it is case-correct and try an exact match.
+ */
 static void handle_path_without_trailing_slash(
 	struct index_state *istate, const char *name, int pos)
 {
-	int i;
-
 	/*
 	 * Mark the untracked cache dirty for this path (regardless of
 	 * whether or not we find an exact match for it in the index).
@@ -200,33 +212,28 @@ static void handle_path_without_trailing_slash(
 
 	if (pos >= 0) {
 		/*
-		 * We have an exact match for this path and can just
-		 * invalidate it.
+		 * An exact match on a tracked file. We assume that we
+		 * do not need to scan forward for a sparse-directory
+		 * cache-entry with the same pathname, nor for a cone
+		 * at that directory. (That is, assume no D/F conflicts.)
 		 */
 		istate->cache[pos]->ce_flags &= ~CE_FSMONITOR_VALID;
 	} else {
+		struct strbuf work_path = STRBUF_INIT;
+
 		/*
-		 * The path is not a tracked file -or- it is a
-		 * directory event on a platform that cannot
-		 * distinguish between file and directory events in
-		 * the event handler, such as Windows.
-		 *
-		 * Scan as if it is a directory and invalidate the
-		 * cone under it.  (But remember to ignore items
-		 * between "name" and "name/", such as "name-" and
-		 * "name.".
+		 * The negative "pos" gives us the suggested insertion
+		 * point for the pathname (without the trailing slash).
+		 * We need to see if there is a directory with that
+		 * prefix, but there can be lots of pathnames between
+		 * "foo" and "foo/" like "foo-" or "foo-bar", so we
+		 * don't want to do our own scan.
 		 */
-		int len = strlen(name);
-		pos = -pos - 1;
-
-		for (i = pos; i < istate->cache_nr; i++) {
-			if (!starts_with(istate->cache[i]->name, name))
-				break;
-			if ((unsigned char)istate->cache[i]->name[len] > '/')
-				break;
-			if (istate->cache[i]->name[len] == '/')
-				istate->cache[i]->ce_flags &= ~CE_FSMONITOR_VALID;
-		}
+		strbuf_add(&work_path, name, strlen(name));
+		strbuf_addch(&work_path, '/');
+		pos = index_name_pos(istate, work_path.buf, work_path.len);
+		handle_path_with_trailing_slash(istate, work_path.buf, pos);
+		strbuf_release(&work_path);
 	}
 }