fix(release): keep automatic releases on the default branch

An automatic release pushes its bump to the branch it ran from, but the Homebrew and prebuilt sync always targets the default branch. Dispatched from anywhere else, the bump and the formula land on different branches and main advertises a version whose bump it never received.

Fail early and say which branch it is on. Releasing another branch keeps working with an explicit tag, where the bump is already committed and nothing has to guess where it belongs.

Author: piotrlaczkowski

.github/workflows/release.yml

@@ -122,8 +122,20 @@ jobs:
         if: github.event_name == 'workflow_dispatch' && inputs.tag == ''
         env:
           BUMP: ${{ inputs.bump }}
+          DEFAULT_BRANCH: ${{ github.event.repository.default_branch }}
         run: |
           set -euo pipefail
+          # An automatic release pushes its bump to the branch it ran from, but
+          # "Sync Homebrew formula + prebuilt binaries" below always targets the
+          # default branch. From anywhere else those two land on different
+          # branches, and main ends up advertising a version whose bump it never
+          # received. Releasing another branch is still possible — with an
+          # explicit tag, where the bump is already committed and nothing here
+          # has to guess where it belongs.
+          if [[ "${GITHUB_REF_NAME}" != "${DEFAULT_BRANCH}" ]]; then
+            echo "::error::an automatic release (empty tag) runs from ${DEFAULT_BRANCH} only — this run is on ${GITHUB_REF_NAME}. Give an explicit tag to release another branch."
+            exit 1
+          fi
           git config user.name "github-actions[bot]"
           git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
           version="$(./scripts/next-version.sh --bump "$BUMP" --explain)"

RELEASE.md

@@ -144,6 +144,11 @@ Cutting 1.0.0 is deliberate, never automatic: on a 0.x line a breaking change mo
 minor. Run `scripts/next-version.sh --bump major --allow-zero-major` locally, commit the
 bump, and release it with an explicit tag.
 
+An automatic release runs from **`main` only**, and says so if you point it elsewhere. It
+pushes its bump to the branch it ran from, while the Homebrew sync always targets `main`;
+from another branch those two would land in different places. Release another branch with
+an explicit tag, where the bump is already committed.
+
 **Give a tag — release a version that is already committed.** For re-running a release
 that published its tag and then died: the job notices the tag exists and builds **from that
 tag**, not from whatever `main` has become since, so the assets still match the commit the