Preserve local metadata with cp_file. Fixes #1524

[Skylion007]

Preserves permissions when copying local file. Fixes #1524

[Skylion007]

@martindurant Is there a place I should add a regression test? I don't see any infra for doing that though for LocalFilesystem.

[Skylion007]

Actually, the more I think about this. The less sure I am about whether it should preserve this copied metadata by default. A lot of os system calls in Python do not... It wouldn't be add as a configuration option though...

[martindurant]

Well... the default implementation for cp (like open(out).write(open(in).read()) ) transfers only data, since it is generic over al backends. I don't think any of the backend cp implementations explicitly transfer metadata, although it may be good to do an audit on this.

posix/bash's cp does not copy all access attributes:

$ chmod a+wrx TEMP
$ cp TEMP TEMP2
$ ll TEMP*
-rwxrwxrwx  1 mdurant  staff  1513  6 Mar 09:29 TEMP
-rwxr-xr-x  1 mdurant  staff  1513  6 Mar 09:29 TEMP2