CI(release): create reusable workflow for releases (#9806)

## Problem

We have a bunch of duplicated code for automated releases. There will be
even more, once we have `release-compute` branch
(https://github.com/neondatabase/neon/pull/9637).

Another issue with the current `release` workflow is that it creates a
PR from the main as is. If we create 2 different releases from the
same commit, GitHub could mix up results from different PRs.

## Summary of changes
- Create a reusable workflow for releases
- Create an empty commit to differentiate releases

.github/workflows/_create-release-pr.yml

@@ -0,0 +1,79 @@
+name: Create Release PR
+
+on:
+  workflow_call:
+    inputs:
+      component-name:
+        description: 'Component name'
+        required: true
+        type: string
+      release-branch:
+        description: 'Release branch'
+        required: true
+        type: string
+    secrets:
+      ci-access-token:
+        description: 'CI access token'
+        required: true
+
+defaults:
+  run:
+    shell: bash -euo pipefail {0}
+
+jobs:
+  create-storage-release-branch:
+    runs-on: ubuntu-22.04
+
+    permissions:
+      contents: write # for `git push`
+
+    steps:
+    - uses: actions/checkout@v4
+      with:
+        ref: main
+
+    - name: Set variables
+      id: vars
+      env:
+        COMPONENT_NAME: ${{ inputs.component-name }}
+        RELEASE_BRANCH: ${{ inputs.release-branch }}
+      run: |
+        today=$(date +'%Y-%m-%d')
+        echo "title=${COMPONENT_NAME} release ${today}" | tee -a ${GITHUB_OUTPUT}
+        echo "rc-branch=rc/${RELEASE_BRANCH}/${today}"  | tee -a ${GITHUB_OUTPUT}
+
+    - name: Configure git
+      run: |
+        git config user.name "github-actions[bot]"
+        git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+
+    - name: Create RC branch
+      env:
+        RC_BRANCH: ${{ steps.vars.outputs.rc-branch }}
+        TITLE: ${{ steps.vars.outputs.title }}
+      run: |
+        git checkout -b "${RC_BRANCH}"
+
+        # create an empty commit to distinguish workflow runs
+        # from other possible releases from the same commit
+        git commit --allow-empty -m "${TITLE}"
+
+        git push origin "${RC_BRANCH}"
+
+    - name: Create a PR into ${{ inputs.release-branch }}
+      env:
+        GH_TOKEN: ${{ secrets.ci-access-token }}
+        RC_BRANCH: ${{ steps.vars.outputs.rc-branch }}
+        RELEASE_BRANCH: ${{ inputs.release-branch }}
+        TITLE: ${{ steps.vars.outputs.title }}
+      run: |
+        cat << EOF > body.md
+          ## ${TITLE}
+
+          **Please merge this Pull Request using 'Create a merge commit' button**
+        EOF
+
+        gh pr create --title "${TITLE}" \
+                     --body-file "body.md" \
+                     --head "${RC_BRANCH}" \
+                     --base "${RELEASE_BRANCH}"

.github/workflows/release.yml

@@ -26,82 +26,26 @@ defaults:
 jobs:
   create-storage-release-branch:
     if: ${{ github.event.schedule == '0 6 * * MON' || format('{0}', inputs.create-storage-release-branch) == 'true' }}
-    runs-on: ubuntu-22.04
 
     permissions:
-      contents: write # for `git push`
+      contents: write
 
-    steps:
-    - name: Check out code
-      uses: actions/checkout@v4
-      with:
-        ref: main
-
-    - name: Set environment variables
-      run: |
-        echo "RELEASE_DATE=$(date +'%Y-%m-%d')" | tee -a $GITHUB_ENV
-        echo "RELEASE_BRANCH=rc/$(date +'%Y-%m-%d')" | tee -a $GITHUB_ENV
-
-    - name: Create release branch
-      run: git checkout -b $RELEASE_BRANCH
-
-    - name: Push new branch
-      run: git push origin $RELEASE_BRANCH
-
-    - name: Create pull request into release
-      env:
-        GH_TOKEN: ${{ secrets.CI_ACCESS_TOKEN }}
-      run: |
-        TITLE="Storage & Compute release ${RELEASE_DATE}"
-
-        cat << EOF > body.md
-          ## ${TITLE}
-
-          **Please merge this Pull Request using 'Create a merge commit' button**
-        EOF
-
-        gh pr create --title "${TITLE}" \
-                     --body-file "body.md" \
-                     --head "${RELEASE_BRANCH}" \
-                     --base "release"
+    uses: ./.github/workflows/_create-release-pr.yml
+    with:
+      component-name: 'Storage & Compute'
+      release-branch: 'release'
+    secrets:
+      ci-access-token: ${{ secrets.CI_ACCESS_TOKEN }}
 
   create-proxy-release-branch:
     if: ${{ github.event.schedule == '0 6 * * THU' || format('{0}', inputs.create-proxy-release-branch) == 'true' }}
-    runs-on: ubuntu-22.04
 
     permissions:
-      contents: write # for `git push`
+      contents: write
 
-    steps:
-    - name: Check out code
-      uses: actions/checkout@v4
-      with:
-        ref: main
-
-    - name: Set environment variables
-      run: |
-        echo "RELEASE_DATE=$(date +'%Y-%m-%d')" | tee -a $GITHUB_ENV
-        echo "RELEASE_BRANCH=rc/proxy/$(date +'%Y-%m-%d')" | tee -a $GITHUB_ENV
-
-    - name: Create release branch
-      run: git checkout -b $RELEASE_BRANCH
-
-    - name: Push new branch
-      run: git push origin $RELEASE_BRANCH
-
-    - name: Create pull request into release
-      env:
-        GH_TOKEN: ${{ secrets.CI_ACCESS_TOKEN }}
-      run: |
-        TITLE="Proxy release ${RELEASE_DATE}"
-
-        cat << EOF > body.md
-          ## ${TITLE}
-
-          **Please merge this Pull Request using 'Create a merge commit' button**
-        EOF
-
-        gh pr create --title "${TITLE}" \
-                     --body-file "body.md" \
-                     --head "${RELEASE_BRANCH}" \
-                     --base "release-proxy"
+    uses: ./.github/workflows/_create-release-pr.yml
+    with:
+      component-name: 'Proxy'
+      release-branch: 'release-proxy'
+    secrets:
+      ci-access-token: ${{ secrets.CI_ACCESS_TOKEN }}