This should be a good place to eventually make use of `_fromstate` depending on
what we're trying to show in this example.

We now have `_fromstate` and `_fromstate_on_head`, the latter of which updates
the current branch to point to the new commit.

Currently git_commit_create() takes on creating a commit and updating a
reference. Provide a better interface by splitting up each of the
concerns into named functions for each.

git_commit_create() will only create the commit, it will not modify any
reference. git_commit_create_on() takes a reference name to update and
git_commit_create_on_head() is a convenience function to update HEAD.

This variant of the commit creation function takes the reference to
update, the tree and the parents from the current branch, index and
merging state, allowing for simpler use of a common use-case.

online tests: update auth for bitbucket test

Update the settings to use a specific read-only token for accessing our
test repositories in Bitbucket.

Refactor `gitno_extract_url_parts`

RFC 3986 says that hostnames can be percent encoded.  Percent decode
hostnames in our URLs.