* Check that PR status is OPEN and not CLOSED or MERGED.
* Display url of PR
* Add parameter --admin-override to merge. Will call the 'gh pr merge'
  command with the --admin option to override required checks if
  possible
* Look for github status checks and stop merge if not successful.
  Provide option --ignore-status-checks in merge to skip this check.

rerunning "pipenv lock" to get newer versions of everything we're using.

pr-tool will now also check if the status check with context
"continuous-integration/jenkins/pr-merge" is present and fail the PR
check otherwise.

"pr-tool merge" will now show if PR was merged or not before exiting.

The headline-check on pr-tool commit now allows up to 60 characters.

Enables pr-tool check to display the section to which the changelog
record will be added.

The pr-tool is now able to select the section to which a ChangeLog entry
should be added based on the PR's labels.
Currently this will only check for the "documentation" label and set the
section to Documentation (which was not possible before).

add_changelog_entry() did a bad job if there were existing multiline
entries in the changelog. If the section where a new entry should be
added ended in something like this:

- normal changelog entry
  - with additional information
  - and more information

it would misdetect the location to add the new record and insert it
after the first line instead of at the end.
Now it also skips lines where "- " is preceded by whitespace.

You can now pass absolute paths as a parameter to --file when running
add-changelog-entry.
The original add-changelog-entry would always interpret its --file
argument relatively to the current git repository, even if the path was
absolute.

The user can override the host or repository for the gh command using
the environment variables GH_HOST or GH_REPO. As we will have to
determine the repository and the name of the remote ourselves (gh does
not provide a way to do that), setting GH_HOST or GH_REPO will probably
break pr-tool at some point, so we disallow it.

Also introduces logging options.

For doing a rebase, we need to know the (remote) branch we're rebasing
onto. While this is usually "origin" you can call it whatever you want.
We now determine the correct git remote in the same fashion as gh cli
does.

When your local repository is not up to date, rebasing (and potentially
other operations) will not lead to the desired result or may even fail.
pr-tool will now check if your local repository's base branch points to
the same commit as the remote repository's base branch and will issue a
warning otherwise.

When checking commits, pr-tool will now look at the local history
instead of the commits in the PR at github. So you can reword and
recheck without pushing.

With this patch, you can now invoke check_sources.main_program() from
your own code and get meaningful results.

When running pr-tool check or pr-tool merge, an automated run of
bareos-check-sources --since=<your-merge-base-commit> happens and its
result is evaluated as a checkmark result for the PR.

As this is now automated, we can remove the checkmark from the PR
template.

By using another approach to detect changed files per commit, the
performance of bareos-check-sources could be drastically improved.

Instead of looking at the mime-type, we now simply check if the file is
empty and try to read it as utf-8 otherwise. This turned out to be
faster than guessing the mime-type first.
We can probably improve this further by adding some filename patterns
that should always be skipped (like *.gz, *.tgz, *.png, *.min.*).

This plugin shrinks block comments by merging alone standing
begin and end of block comments (/* and */) into the second and in the
last line, respectively.

Block comments starting in the first column remain untouched, as these
are usually file license information or function documentation.

Ran rm Pipfile.lock && pipenv install