[kammce]

Fixes the 📚 Deploy APIs runs that fail at "Deploy to API repo" with a non-fast-forward push. libhal and libhal-arm-mcu both fail this way on main right now.

Cause

api_deploy.py cloned libhal/api, created the docs branch from main, then ran git pull origin <branch>.

• When main has a commit the docs branch lacks, the two have diverged, and the pull fails because no pull strategy is configured.
• That happens whenever another repository's docs PR merges while this repository's docs PR is still open. Today, Add scatter_span main API documentation api#109 (scatter_span) merged while ✨ Add latest library builds to app_builder2.yml #107 (libhal) and 👷 Use multiarch gcc profile for baremetal packages #108 (libhal-arm-mcu) were open.
• The script reported the failed pull as "No existing remote branch", committed on top of main, and the push was rejected.

Change

• If origin/<branch> exists, the script checks it out and commits on top, so the push is a fast-forward.
• If it doesn't exist, the branch starts from main as before.
• Being behind main doesn't matter for the docs PR, since each repository's docs live in their own directory.

Testing

I tested locally against a bare repo set up the way libhal/api is now: a docs branch one commit behind a main that moved on. The GitHub URL and API calls were stubbed out.

• The old script fails with the same non-fast-forward rejection as CI.
• The new script commits on top of the existing branch and pushes.
• For a repository with no docs branch, the new script starts from main and pushes.

[kammce]

lgtm