PR to open project without write access

Whenever I want to create pull requests to a repo that I don't have write access to, I:

1. Fork the original repo to my account.
2. Clone the original repo to my local machine.
3. Add my fork as an additional remote and make it the push default.
4. Make changes in a new branch locally.
5. Push this branch to my fork.
6. Create a pull request from there.

```
git clone https://github.com/<origin_org>/<repo_name>.git
cd <repo_name>
git remote add fork https://github.com/<your_name>/<your_repo>.git
git config remote.pushDefault fork
```

This way, at a later time point I can easily:

1. Pull changes from origin into the local master branch.
2. Create another contribution branch.
3. Push that to my fork.
4. Create a new pull request.

```
cd <repo_name>
git checkout master
git pull
git push # update the fork, which can be relevant for continuous integration checking against the master branch
git checkout -b new-contribution-branch
# make changes and commit
git push
```

## Sources:
* Setting the push default: <https://stackoverflow.com/a/30488025>