How to set Subversion properties with git-svn

Note: git 2.3.0 (February 2015) supports proset with git svn.
See commit 83c9433 by Alfred Perlstein (splbio):

git-svn: support for git-svn propset

This change allows git-svn to support setting subversion properties.

It is useful for manually setting properties when committing to a subversion repo that requires properties to be set without requiring moving your changeset to separate subversion checkout in order to set props.

There is a nit to point out: the code does not support adding props unless there are also content changes to the files as well.
This is demonstrated in the testcase.

So, as seen in t/t9148-git-svn-propset.sh, this now works:

git svn propset "$1" "$2" "$file" 
# like
git svn propset "svn:keywords" "FreeBSD=%H" "foo"