properly handle empty log messages
properly handle multiline headers in commits
new gpgsig and mergetag accessors for Git::Repository::Log
Some notes about the initialisation data for Git::Repository::Log
test Git::Repository::Plugin::Log with multiline headers

the multiline.bundle Git bundle contains a specialy crafted
repository with:
- an empty tree
- an empty log message
- a commit with non-utf8 encoding
- a signed commit
- a mergetag commit
Changes for version 1.302