GitPlugin not working

[mendelso@…]

The plug-in looks like it loads

from log/trac.log

2012-05-30 16:18:40,092 Trac[env] INFO: -------------------------------- environment startup [Trac 0.12.3] --------------------------------
2012-05-30 16:18:40,107 Trac[loader] DEBUG: Loading git from /Library/Python/2.7/site-packages/TracGit-0.12.0.5dev-py2.7.egg

But then the web page returns

Warning: Can't synchronize with repository "(default)" (/Users/mpm/demo/git/example.git does not appear to be a Subversion repository.). Look in the Trac log for more information. 

conf/trac.ini has the following

[components]
tracopt.versioncontrol.git.* = enabled

[trac]
repository_dir = /Users/mpm/demo/git/example.git
repository_type = git

[git]
## let Trac cache meta-data via CachedRepository wrapper; default: false
# cached_repository = true
cached_repository = false

## disable automatic garbage collection for in-memory commit-tree cache; default: false
# persistent_cache = true
persistent_cache = false

## length revision sha-sums should be tried to be abbreviated to (must be >= 4 and <= 40); default: 7
shortrev_len = 6

## minimum length for which hex-strings will be interpreted as commit ids in wiki context; default: 40
wiki_shortrev_len = 7

## executable file name (in case of doubt use absolute path!) of git binary; default: 'git'
git_bin = /opt/local/bin/git

## define charset encoding of paths stored within git repository; default: 'utf-8'
git_fs_encoding = latin1

## enable reverse mapping of git email addresses to trac user ids; default: false
trac_user_rlookup = true

## use git-committer id instead of git-author id as changeset owner; default: true
use_committer_id = false

## use git-committer timestamp instead of git-author timestamp as changeset time; default: true
use_committer_time = false