Thanks for publishing this action.
I followed the readme instructions but ran into what may be a common but undocumented case.
I'm publishing for the first time and no gh-pages branch exists.
The action proceeds to stage changes but they never get pushed to my PUBLISH_BRANCH
Cloning into '/github/home/b8c542550a778e3eb0ca70abff3d5482'...
warning: Could not find remote branch gh-pages to clone.
fatal: Remote branch gh-pages not found in upstream origin
Initialized empty Git repository in /github/workspace/target/doc/.git/
Switched to a new branch 'gh-pages'
fatal: No such remote: 'origin'
INFO: Allowing empty commits:
[gh-pages (root-commit) 975a973] Automated deployment: Sun Sep 22 04:26:54 UTC 2019 3a9dc85d243d35fe33b4992ae2a042c6793e8861
131 files changed, 15230 insertions(+)
create mode 100755 .lock
...more files...