Add format action

.github/workflows/format.yml

@@ -0,0 +1,35 @@
+name: format code
+on:
+  pull_request:
+
+jobs:
+  format-code:
+    name: Format Code
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        package: [flutter, dart]
+    defaults:
+      run:
+        working-directory: ${{ matrix.package }}
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dart-lang/setup-dart@6a218f2413a3e78e9087f638a238f6b40893203d # pin@v1
+        if: ${{ matrix.package == 'dart' }}
+      - uses: subosito/flutter-action@48cafc24713cca54bbe03cdc3a423187d413aafa # pin@v2.10.0
+        if: ${{ matrix.package == 'flutter' }}
+
+      - name: pub get
+        run: ${{ matrix.package }} pub get
+
+      - name: format
+        run: dart format .
+
+      - name: fix
+        run: dart fix --apply
+
+      # actions/checkout fetches only a single commit in a detached HEAD state. Therefore
+      # we need to pass the current branch, otherwise we can't commit the changes.
+      # GITHUB_HEAD_REF is the name of the head branch. GitHub Actions only sets this for PRs.
+      - name: Commit & Push
+        run: ../scripts/commit-formatted-code.sh $GITHUB_HEAD_REF

scripts/commit-formatted-code.sh

@@ -0,0 +1,16 @@
+#!/bin/bash
+set -euo pipefail
+
+GITHUB_BRANCH="${1}"
+
+if [[ $(git status) == *"nothing to commit"* ]]; then
+    echo "Nothing to commit. All code formatted correctly."
+else
+    echo "Formatted some code. Going to push the changes."
+    git config --global user.name 'Sentry Github Bot'
+    git config --global user.email 'bot+github-bot@sentry.io'
+    git fetch
+    git checkout ${GITHUB_BRANCH}
+    git commit -am "Format & fix code"
+    git push --set-upstream origin ${GITHUB_BRANCH}
+fi