hgsubversion: fix naming and dependencies

[macports.org@…]

hgsubversion is currently called py26-hgsubversion and depends on:

• mercurial
• python26
• subversion-python26bindings

This is troublesome, because mercurial's python dependency was changed to 2.7, meaning hgsubversion now needs subversion-python27bindings (or py27-subvertpy both will work) and does *not* need either python26 or subversion-python26bindings, but this is not handled by macports and will instead break at runtime:

> hg clone http://fbug.googlecode.com/svn/
destination directory: svn
abort: no compatible bindings available:

Subversion 1.5.0 or later required, but no bindings were found
Subvertpy 0.7.4 or later required, but not found

Please install either Subvertpy or the Subversion Python SWIG bindings!

• The direct Python dependency should be removed from hgsubversion (hgsubversion gets it transitively via the dependency on mercurial)
• hgsubversion should depend on "the subversion-python*bindings corresponding to hg's Python dependency" if it's possible to express such a complex dependency
• A variant should be added replacing the dependency on subversion-python*bindings by a dependency on py*-subvertpy

[titus@…]

Cc Me!

[titus@…]

Apparently, there is no way to make a generic port hgsubversion that pulls in the python version used by mercurial.

[titus@…]

r87987

Implemented py27-hgsubversion and marked py26-hgsubversion replaced_by it.