[merge] Tweaks for AtomicFile and LocalTransport.append()

[Martin Pool]

On  9 Aug 2006, John Arbash Meinel <john at arbash-meinel.com> wrote:
> The attached patches tweak AtomicFile and LocalTransport.append and
> mkdir so that hopefully they will ultimately do fewer chmod() calls. In
> general, it streamlines a few code paths. The final performance
> difference can be seen with 'make_kernel_like_tree'.
> 
> On my machine 'make_kernel_like_tree' takes:
>   bzr.dev:		7.8 - 8.2
>   with tweaks and put:	4.5 - 7.5
>   switching to append:  2.9 - 4.5
> 
> I'm not really interested in the make_kernel_like_tree improvements,
> since my benchmark caching will handle that even better. However, it
> does show a general improvement in LocalTransport.put() and append()
> speeds, which I am very interested in.
> 
> Robert started this work. I just cleaned it up, added direct tests for
> AtomicFile, and made sure that file modes still worked correctly even
> when umask is involved.

+1

This reminds me we should finish off and merge the refinements to
TestSkipped that Aaron was working on.

-- 
Martin