[PATCH 07 of 10] util: implement a faster os.path.split for posix systems

[Greg Ward]

On 13 September 2012, Bryan O'Sullivan said:
> # HG changeset patch
> # User Bryan O'Sullivan <bryano at fb.com>
> # Date 1347562630 25200
> # Node ID 9d1ceb24dc23a965d6df2b14ebca30da59139710
> # Parent  38159ce2f0115498a0c43b4c84a3f9ba87d08561
> util: implement a faster os.path.split for posix systems

Measurable speedup?

> diff --git a/mercurial/posix.py b/mercurial/posix.py
> --- a/mercurial/posix.py
> +++ b/mercurial/posix.py
> @@ -20,6 +20,16 @@
>  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
> +

-1 on the cryptic variable names. If "ht" means "headtail", why not
say "headtail"? It really does make things easier to read.

And this kind of thing is The Ultimate Poster Child for unit testing.
Yeah, yeah, I know, Mercurial doesn't do unit testing. But some of
those test-*.py scripts are an awful lot like unit testing, so
apparently it's not completely verboten. Time for test-posix.py?

       Greg