I installed git-svn the other day with an out-of-date MacPorts index, and wound up with version 1.5.3.7 installed.  It turns out that 'git svn info', which is used by post-review to find repository information, wasn't added until git 1.5.4 (see http://www.kernel.org/pub/software/scm/git/docs/RelNotes-1.5.4.txt ).  This adds a version check for git-svn which is run if git svn info fails, and which lets the user know that the git-svn version is out of date.

Tested against my old 1.5.3.7 install and my new, hotter 1.5.4.4 install.