util.makedirs: make recursion simpler and more stable (issue2948)

Before, makedirs could call itself recursively with the same path name it was
given, relying on sane file system behavior to terminate the recursion. That
could cause infinite recursion on insane file systems.

Instead we now call mkdir explicitly after having created parent directory
recursively. Exceptions from this mkdir is not swallowed.

mercurial/util.py

@@ -789,7 +789,7 b' def makedirs(name, mode=None):'
         if not name or parent == name or err.errno != errno.ENOENT:
             raise
         makedirs(parent, mode)
-        makedirs(name, mode)
+        os.mkdir(name)
     if mode is not None:
         os.chmod(name, mode)