I don't get how it was working without git_libgit2_init() call. I run it
and libgit2 throws assertion somewhere in its internals. Now it works.
Updated commit with shutdown at the end.
This is quite close to running "git for-each-ref" except:
1. It does not take any formatting or selection options at
all.
2. The output is not sorted.
I wrote it to look at debugging some issues with ref
iteration, but there's no reason it can't live on as an
example command.
