1. The license header is technically not valid if it doesn't have a
copyright signature.
2. The COPYING file has been updated with the different licenses used in
the project.
3. The full GPLv2 header in each file annoys me.
So far libgit2 didn't support reference logs (reflog). Add a new
git_reflog_* API for basic reading and writing of reflogs:
* git_reflog_read
* git_reflog_write
* git_reflog_free
Signed-off-by: schu <schu-github@schulog.org>