pathspec: rename free_pathspec() to clear_pathspec()

The function takes a pointer to a pathspec structure, and releases
the resources held by it, but does not free() the structure itself.
Such a function should be called "clear", not "free".

Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/notes-merge.c b/notes-merge.c
index 34bfac0..b7814c9 100644
--- a/notes-merge.c
+++ b/notes-merge.c
@@ -170,7 +170,7 @@
 		       sha1_to_hex(mp->remote));
 	}
 	diff_flush(&opt);
-	free_pathspec(&opt.pathspec);
+	clear_pathspec(&opt.pathspec);
 
 	*num_changes = len;
 	return changes;
@@ -256,7 +256,7 @@
 		       sha1_to_hex(mp->local));
 	}
 	diff_flush(&opt);
-	free_pathspec(&opt.pathspec);
+	clear_pathspec(&opt.pathspec);
 }
 
 static void check_notes_merge_worktree(struct notes_merge_options *o)