Very minor changes

• Fork repository
• Create a branch
• Commit and push change
• File a pull request

If you observe an issue and have an idea how to fix it

• Open an issue in the repository you wish to contribute to
• Describe the problem
• If you have a suggestion on how to fix it, describe your suggestion
• Possibly discuss and get feedback
• If you are working on the fix, indicate it in the issue so that others know that somebody is working on it and who is working on it
• Submit your fix as pull request which references/closes the issue

Motivation:

• Inform others about an observed problem
• Make it clear whether this issue is up for grabs or already being worked on

If you have an idea for a new feature

• Open an issue in the repository you wish to contribute to
• Write a short proposal for your suggested change or new feature
• Motivate why and how you wish to do this
• Discuss and get feedback before you code
• Once you start coding, indicate that you are working on it
• Once you are done, submit your new feature as pull request which references/closes the issue/proposal

Motivation:

• Get agreement and feedback before writing 5000 lines of code which might be rejected
• If we later wonder why something was done, we have the proposal as reference and can read up on the reasoning behind a code change

WIP (work in progress) merge requests and draft pull requests

• Convention: Pull requests or merge requests starting with “WIP” are not to be merged yet
• They are there to collect feedback on unfinished work
• On GitHub you can create draft pull requests which cannot be merged until marked ready for review.

Motivation:

• Get agreement and feedback before writing 5000 lines of code which might be rejected
• If we later wonder why something was done, we have the proposal as reference and can read up on the reasoning behind a code change

Licenses matter

• If you submit code that is derivative work or code somebody else wrote, clarify license
• If you receive pull requests with a lot of code, clarify its license and copyright

How to make sure that you don’t merge malicious code

(this is typically not a problem for most of us but can be a problem for some)

• Since commit hashes depend on all their parents you cannot modify the past without all future hashes changing
• Projects like https://github.com/torvalds/linux or https://github.com/bitcoin/bitcoin have to be extremely careful what they accept
• Do not blindly merge submitted pull requests
• Browse the code changes before merging them
• If you get an extremely large changeset, ask for more information
• Possibly verify whether the submitter is not trying to impersonate somebody you know
• Git commits can be PGP signed to verify authenticity