[rfc] Proposal: fake symlinks support on windows

[Aaron Bentley]

Alexander Belchenko wrote:
> Today I'm playing a bit with cygwin, ssh and paramiko.
> And I faced with symlinks.
> 
> I propose reuse cygwin format and gain full compatibility with cygwin.
> 
> I propose to make special methods in bzrlib/osutils.py module:
> 
> bzrlib.osutils.readlink  -> extract file path from fake symlink
> bzrlib.osutils.symlink   -> create fake symlink


> that will simulate work with symlinks for native windows. This methods
> for all other systems that has support of symlinks should be
> transparently directed to
> 
> bzrlib.osutils.readlink = os.readlink
> bzrlib.osutils.readlink = os.symlink

I don't think they should go there, because if we switch on platform, 
*nix won't handle these symlinks properly (i.e. if the tree is created 
by Windows, then accessed by *nix.)

I think the symlink-handling approach should be per-working tree, and 
that *nix should use this style when working with a tree that was 
created by Windows.

I think your proposal can be usefully combined with 
http://bazaar-vcs.org/WindowsSymlinkSupport

> Also it require to have more intelligent detection of file type on
> windows (during add), i.e. plain files with system attribute should be
> checked for '!<symlink>...\0' signature.
> 
> I think it doable. Because I need fake symlink support for my
> inter-platform work, I want to implement this approach. May be a little
> help and hints needed.

That sounds doable.  It's nice that it will work with cygwin's symlink 
implementation, though of course cygwin doesn't need special support 
from bzr.

Aaron