Fix: Get the default branch from env vars also allow to overwrite as parameter

[sbe-arg]

Hotfix

[sbe-arg]

I'm back lets merge this

[martinjlowm]

This broke our CI with:

The DEFAULT_BRANCH should be autodetected when tag-action runs on on PRs else must be defined, See: https://github.com/anothrNick/github-tag-action/pull/230, since is not defined we find it natively
fatal: ref refs/remotes/origin/HEAD is not a symbolic ref
default_branch=

Apparently, the GITHUB_BASE_REF fallback is empty as well.

[JP-Dhabolt]

@sbe-arg @sammcj
This change was not backwards compatible and broke our CI as well.

The DEFAULT_BRANCH should be autodetected when tag-action runs on on PRs else must be defined, See: https://github.com/anothrNick/github-tag-action/pull/230, since is not defined we find it natively
fatal: ref refs/remotes/origin/HEAD is not a symbolic ref
default_branch=
Error: DEFAULT_BRANCH must not be null, something has gone wrong.

Edit: I commented here, as this is where the error message linked to, but I actually think it is #235 that broke things, as #235 introduced the exit 1.

[Drew-Kimberly]

+1 to the above. This change broke our CI as well w/ the same error

[PrakharSrivastav]

+1 . Broke the existing CI

[afranzoy]

+1. Broke our CI pipenline with the error: "DEFAULT_BRANCH must not be null, something has gone wrong."

[sonyavera]

+1

[artem-tomyuk]

+1

[sammcj]

This project badly needs tests, especially if folks are going to run the action from main.

@sbe-arg please revert

[sammcj]

If anyone here is/was affected by this breaking change, has development (or test automation) skills and is interested to helping to maintain this project - please let me or @sbe-arg know on the following issue - #238

This project isn't ours, we've just been added as contributors because it went unmaintained for some time. The project doesn't have reasonable test coverage (see #184), which is in part why we suggest people don't run it from main/master unless you're happy to be testing cutting edge changes.

We're only two folks, in the same time zone so it's currently very much a best effort as we both work full time and have social lives etc...

See #238