util: implement a faster os.path.split for posix systems

This is not yet used.

mercurial/posix.py

@@ -20,6 +20,16 b' expandglobs = False'
 umask = os.umask(0)
 os.umask(umask)
 
+def split(p):
+    '''Same as os.path.split, but faster'''
+    ht = p.rsplit('/', 1)
+    if len(ht) == 1:
+        return '', p
+    nh = ht[0].rstrip('/')
+    if nh:
+        return nh, ht[1]
+    return ht
+
 def openhardlinks():
     '''return true if it is safe to hold open file handles to hardlinks'''
     return True

mercurial/util.py

@@ -62,6 +62,7 b' setflags = platform.setflags'
 setsignalhandler = platform.setsignalhandler
 shellquote = platform.shellquote
 spawndetached = platform.spawndetached
+split = platform.split
 sshargs = platform.sshargs
 statfiles = platform.statfiles
 termwidth = platform.termwidth

mercurial/windows.py

@@ -20,6 +20,7 b' samedevice = win32.samedevice'
 samefile = win32.samefile
 setsignalhandler = win32.setsignalhandler
 spawndetached = win32.spawndetached
+split = os.path.split
 termwidth = win32.termwidth
 testpid = win32.testpid
 unlink = win32.unlink