EDIT: Updated to reference gh correctly. Thanks flod!

Sometimes on Github, I need to fetch a patch from a fork I don't typically see everyday so I can try it out locally. I use the line at the top of the patch which has a copy button next to it because it's convenient.

The common steps for this are:

1. Click the contributor's branch and go to their github fork repository.
2. Copy the repository link.
3. Add a new git remote with an alias (typically their username).
4. git fetch <alias>
5. git checkout <alias>/<branch>

Here is a one-liner for it that you can add to your gitconfig:

[alias]
  co = "!f() { PNAME=$(basename `git rev-parse --show-toplevel`); OWNER=$(echo $1 | cut -d':' -f1); BRANCH=$(echo $1 | cut -d':' -f2); git fetch [email protected]:$OWNER/$PNAME.git $BRANCH; git checkout FETCH_HEAD; }; f"

You might ask, why do all of this when the github gh CLI does this for you? While it does simplify some tasks, I wanted a solution that was independant to a specific git host. The [email protected] remote that is used in the alias can be changed or made configurable if desired. This is something that I wouldn't be able to do with platform-dependant gh.

The fetch also works well with jj too because the fetch and checkout remain headless.

Formatted and commented, it looks less intimidating:

f() {
  # Get the repository name from your checkout (assuming it is the
  # original directory name as the remote).
  PNAME=$(basename `git rev-parse --show-toplevel`);

  # Parse out the fork's owner.
  # Example: `<owner>:<branch>`
  OWNER=$(echo $1 | cut -d':' -f1);

  # Parse out the branch name.
  # Example: `<owner>:<branch>`
  BRANCH=$(echo $1 | cut -d':' -f2);

  # Do a fetch of that particular branch using the extracted
  # information from above.
  # This assumes the remote is hosted on github.
  git fetch [email protected]:$OWNER/$PNAME.git $BRANCH;

  # Checkout using the alias `FETCH_HEAD` which git provides.
  git checkout FETCH_HEAD;
};

# Execute the function!
# It's easier to build a function that holds variables and execute
# rather than in-line it.
f