pr-tool: give hint about commit headline length limits

[joergsteffens]

Thank you for contributing to the Bareos Project!

I already wondered several times, about how long headline could be. Changed the code to give a hint. Decided not to mention the 50, to keep the remark as short as possible.

Please check

• Short description and the purpose of this PR is present above this paragraph
• Your name is present in the AUTHORS file (optional)

If you have any questions or problems, please give a comment in the PR.

Helpful documentation and best practices

• Git Workflow
• Automatic Sourcecode Formatting
• Check your commit messages
• Boy Scout Rule

Checklist for the reviewer of the PR (will be processed by the Bareos team)

Make sure you check/merge the PR using devtools/pr-tool to have some simple automated checks run and a proper changelog record added.

General

• Is the PR title usable as CHANGELOG entry?
• Purpose of the PR is understood
• Commit descriptions are understandable and well formatted
  Required backport PRs have been created

Source code quality

• Source code changes are understandable
• Variable and function names are meaningful
• Code comments are correct (logically and spelling)
• Required documentation changes are present and part of the PR

[sebsura]

Nice change!

[sebsura]

Could you fix the type in the first commit headline ? lenght -> length

[joergsteffens]

Fixed type and squashed commits.