wip: add target-branch-pattern

Author: jimeh

action.yml

@@ -58,11 +58,15 @@ inputs:
       Branch to open pull release PR against. Defaults to the repository's
       default branch.
     default: ""
-  maintenance-branch-pattern:
+  target-branch-pattern:
     description: >-
-      Regex pattern for maintenance branches. Defaults to `^release-[0-9]+(\.[0-9]+)?\.x$`.
-    default: |-
-      ^release-[0-9]+(\.[0-9]+)?\.x$
+      Regular expression pattern to determine if current branch is a target
+      branch. When specified, the action will only run if the current branch
+      matches the pattern, and the current branch will be used as the target
+      branch. When not specified, the action will always run, and target the
+      specified target-branch, or the repository's default branch if
+      target-branch is not specified.
+    default: ""
   config-file:
     description: Path to config file within the project.
     default: ".github/release-please-config.json"
@@ -138,8 +142,26 @@ outputs:
 runs:
   using: "composite"
   steps:
+    - name: prepare
+      shell: bash
+      id: prepare
+      run: |
+        if [[ -n "$TARGET_BRANCH_PATTERN" ]]; then
+          if [[ "$GITHUB_REF_NAME" =~ $TARGET_BRANCH_PATTERN ]]; then
+            RUN="true"
+            TARGET="$GITHUB_REF_NAME"
+          fi
+        else
+          RUN="true"
+        fi
+
+        echo "target_branch=${TARGET:-$TARGET_BRANCH}" >> "$GITHUB_OUTPUT"
+        echo "run=${RUN:-false}" >> "$GITHUB_OUTPUT"
+      env:
+        TARGET_BRANCH: "${{ inputs.target-branch }}"
+        TARGET_BRANCH_PATTERN: "${{ inputs.target-branch-pattern }}"
     - uses: tibdex/github-app-token@v2
-      if: inputs.app-id != null && inputs.app-id != ''
+      if: steps.prepare.outputs.run == 'true' && inputs.app-id != null && inputs.app-id != ''
       id: github-app-token
       with:
         app_id: ${{ inputs.app-id }}
@@ -151,27 +173,20 @@ runs:
         repositories: ${{ inputs.repositories }}
         revoke: true
     - name: resolve token
+      if: steps.prepare.outputs.run == 'true'
       id: token
+      shell: bash
       run: |-
         echo "token=${APP_TOKEN:-$INPUT_TOKEN}" >> "$GITHUB_OUTPUT"
       env:
         APP_TOKEN: "${{ steps.github-app-token.outputs.token }}"
         INPUT_TOKEN: "${{ inputs.token }}"
-      shell: bash
-    - name: determine target-branch
-      id: branch
-      run: |
-        if [[ -z "${{ inputs.target-branch }}" ]] && [[ "${{ github.ref_name }}" =~ ${{ inputs.maintenance-branch-pattern }} ]]; then
-          echo "target_branch=${{ github.ref_name }}" >> "$GITHUB_OUTPUT"
-        else
-          echo "target_branch=${{ inputs.target-branch }}" >> "$GITHUB_OUTPUT"
-        fi
-      shell: bash
     - uses: googleapis/release-please-action@v4
+      if: steps.prepare.outputs.run == 'true'
       id: release-please
       with:
         token: ${{ steps.token.outputs.token }}
-        target-branch: ${{ steps.branch.outputs.target_branch }}
+        target-branch: ${{ steps.prepare.outputs.target_branch }}
         config-file: ${{ inputs.config-file }}
         manifest-file: ${{ inputs.manifest-file }}
         github-api-url: ${{ inputs.github-api-url }}