[BUG] git-svn parses --pretty=medium log output, fails when log.decorate is true

I started receiving this error during "git svn dcommit" today:

Use of uninitialized value $hash in string eq at /home/wpalmer/libexec/git-core/git-svn line 1534.

Examining that section reveals that git-svn is running "git log --no-color --first-parent --pretty=medium"

and parsing the output in order to find commit hashes and git-svn-id: lines. This breaks when log.decorate is true.

This could be patched-up by adding "--no-decorate" to the options git-svn passes, but that seems to me like it would just be adding to the pile, as "--pretty=medium" is a moving target. I assume the correct solution is to specify the format exactly as it is expected.