Leopard breaking MacPorts git over ssh

As I have been twitting recently, git over ssh stopped working for me after the upgrade to Leopard:

$ git pull
percent_expand: NULL replacement
fatal: The remote end hung up unexpectedly
Cannot get the repository state from ssh://git.mojain.com/...

A quick google search quickly turned up the answer. The problem was not with git, but with ssh. Spefically, ssh from MacPorts. It’s worth noting that ssh in OS X 10.5 is not broken (which made my intial trouble-shooting harder, as ssh-ing from the command line worked just fine). But git in MacPorts is:

$ which ssh
$ ssh git.mojain.com
Last login: Mon Oct 29 20:17:47 2007 from ...
$ ^D

$ /opt/local/bin/ssh git.mojain.com
percent_expand: NULL replacement

You can follow the google results above for the details, but essentially it seems that two things cause the git problem:

  1. Leopard changed some environment variables that caused the MacPorts version of git to get a NULL when it tried to determine what “identity” to use.

  2. git looks for ssh in the same directory as the git binary, causing it to find the MacPorts version before the “native” OS X version.

There are a number of ways to work around this problem (all found in the aforemetioned google results):

  1. Set GIT_SSH to the OS X version (/usr/bin/ssh). This works for git only of course.

  2. Rename your ssh key files so MacPorts ssh can find them (I didn’t try this).

  3. Tell ssh which key file to use by adding the following line to $HOME/.ssh/config (creating that file if it doesn’t exist):

    IdentityFile ~/.ssh/id_dsa

This last option is the one I chose, as it has the advantage of working for all versions and invocations of ssh, and is probably a good idea anyway. Presumably the MacPorts ssh package will be fixed at some point, but this is working for me now.