revision.c: explain what tree_difference does

diff --git a/builtin-rev-parse.c b/builtin-rev-parse.c
index a1c341112185ec4e53dfd2fc0b6f1868e6c5b754..37addb25fafbedba9bad6e99746ee65bacdee7d3 100644 (file)
--- a/builtin-rev-parse.c
+++ b/builtin-rev-parse.c
@@ -233,7 +233,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
                        }
                        continue;
                }
-               if (!strncmp(arg,"-n",2)) {
+               if (!prefixcmp(arg, "-n")) {
                        if ((filter & DO_FLAGS) && (filter & DO_REVS))
                                show(arg);
                        continue;