dirs: add comment about _PyBytes_Resize
So readers have a canonical function to compare this code to.
--- a/mercurial/dirs.c Tue Oct 11 01:29:08 2016 +0200
+++ b/mercurial/dirs.c Thu Oct 13 10:59:29 2016 +0200
@@ -59,7 +59,8 @@
* "protocol" such as mutating immutable objects. But since we only
* mutate objects created in this function or in other well-defined
* locations, the references are known so these violations should go
- * unnoticed. */
+ * unnoticed. The code for adjusting the length of a PyBytesObject is
+ * essentially a minimal version of _PyBytes_Resize. */
while ((pos = _finddir(cpath, pos - 1)) != -1) {
PyObject *val;