If I run "git push" with the GIT_TRACE=2 environment variable, I get the following:
09:25:28.098743 git.c:349 trace: built-in: git 'push' 'origin' 'master'
09:25:28.100261 run-command.c:341 trace: run_command: 'ssh' 'email@example.com' 'git-receive-pack '\''kevinburke/letter.git'\'''
fatal: Could not read from remote repository.
-v Verbose mode. Causes ssh to print debugging messages about its progress.
This is helpful in debugging connection, authentication, and configuration
problems. Multiple -v options increase the verbosity. The maximum is 3.
Put this in your ~/.ssh/config file:
Host <git server> LogLevel (QUIET|FATAL|ERROR|INFO|VERBOSE|DEBUG|DEBUG1|DEBUG2|DEBUG3)
Subsequent git commands that interact with the server should produce desired debug output.