A branch is considered already pushed if its HEAD commit hash matches the commit hash of one of the remote tracking branches: refs/remotes/<remote>/<branch>

This mechanism allows the user to:

• Choose a remote as push target for their branch different than the one that would automatically get chosen for them by pr create;
• Avoid a git push operation (and its associated git hooks) if a push was not necessary in the first place.

Drawbacks:

• If an older version of the branch is pushed to a remote, but later some new commits were added to the local branch, the existing remote tracking branch will intentionally not be considered a push target. This conservative approach is to avoid false positives due to:
  • One of the remotes having an unrelated branch that just so happens to share the same name as the local branch;
  • The local branch being created with a remote tracking branch as a starting point, e.g. git switch -c my-feature origin/master. With git default settings, this will auto-setup merge configuration (see branch.autoSetupMerge in git config), which gh could potentially falsely interpret as a push configuration as well, be it not for the strict commit hash matching.

Fixes #681
Ref. #684 #350 #684

TODO:

• Consider addressing Detect push target for local branches without upstream configuration #575 in this PR as well