This ensures commit->message is always non-NULL, even if the commit
message is empty or consists of only a newline.
One such commit can be found in the wild in the jQuery repository:
25b424134f
The constructor to git_repository is now called
'git_repository_open(path)'
and takes a path to a git repository instead of an existing ODB object.
Unit tests have been updated accordingly and the two test repositories
have been merged into one.
Signed-off-by: Vicent Marti <tanoku@gmail.com>