git svn propset support

Hi

I've been trying to hack at getting manually property setting support for git-svn.

I've got a start of a patch that basically stores an attribute 'svn-properties' for each file that needs them changed, and then sets the properties when committing.

Issues remaining:
 * The way it edits the .gitattributes file is suboptimal - it just appends to the end the latest version
 * It could use the existing code to get the current svn properties to see if properties need to be changed; but this doesn't work on add
 * It would be better to cache all the svn properties locally - this could be done automatically in .gitattributes but I'm not sure everyone would want this, etc
 * No support for deleting properties

Usage is:
 git svn propset PROPNAME PROPVALUE PATH

Patch attached (against 1.6.0.2) - any comments welcome

David

-- 
David Fraser
St James Software