fix: get content hash for master on local engine branches (flutter#172792)

The content hash doesn't exist for local engine changes, except for on
CI. If we detect we're on a branch with committed or uncommitted changes
to engine files; use "master".

towards  flutter#171790

Author: jtmcdole

.github/workflows/content-aware-hash.yml

@@ -13,14 +13,12 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      - name: Fetch base commit and origin/master
-        run: |
-          git fetch --no-tags --prune --depth=1 origin ${{ github.event.pull_request.base.sha }}
-
       - name: Generate Hash
         run: |
-          engine_content_hash=$(bin/internal/content_aware_hash.sh)
+          # IMPORTANT: Keep the list of files in sync with bin/internal/content_aware_hash.sh
+          # We call this directly here as we're expected to be in the merge queue (not master)
+          engine_content_hash=$(git ls-tree --format "%(objectname) %(path)" HEAD -- DEPS engine bin/internal/release-candidate-branch.version | git hash-object --stdin)
           # test notice annotation for retrival from api
           echo "::notice ::{\"engine_content_hash\": \"${engine_content_hash}\"}"
           # test summary writing
-          echo "{\"engine_content_hash\": \"${engine_content_hash}\"" >> $GITHUB_STEP_SUMMARY
+          echo "{\"engine_content_hash\": \"${engine_content_hash}\"" >> $GITHUB_STEP_SUMMARY

bin/internal/content_aware_hash.ps1

@@ -36,6 +36,28 @@ $flutterRoot = (Get-Item $progName).parent.parent.FullName
 # 3. Out-File -NoNewline -Encoding ascii outputs 8bit ascii
 # 4. git hash-object with stdin from a pipeline consumes UTF-16, so consume
 #.   the contents of hash.txt
-(git -C "$flutterRoot" ls-tree --format "%(objectname) %(path)" HEAD DEPS engine bin/internal/release-candidate-branch.version | Out-String) -replace "`r`n", "`n"  | Out-File -NoNewline -Encoding ascii hash.txt
+$trackedFiles = "DEPS", "engine", "bin/internal/release-candidate-branch.version"
+$baseRef = "HEAD"
+
+$ErrorActionPreference = "Continue"
+# We will fallback to origin/master if upstream is not detected.
+git -C "$flutterRoot" remote get-url upstream *> $null
+$exitCode = $?
+$ErrorActionPreference = "Stop"
+if ($exitCode) {
+    $mergeBase = (git -C "$flutterRoot"  merge-base HEAD upstream/master)
+} else {
+    $mergeBase = (git -C "$flutterRoot"  merge-base HEAD origin/master)
+}
+
+# Check to see if we're in a local development branch and the branch has any
+# changes to engine code - including non-committed changes.
+if ((git -C "$flutterRoot" rev-parse --abbrev-ref HEAD) -ne "master") {
+    git -C "$flutterRoot" diff --quiet "$(git -C "$flutterRoot" merge-base $mergeBase HEAD)" -- $trackedFiles | Out-Null
+    if ($LASTEXITCODE -ne 0) {
+        $baseRef = "$mergeBase"
+    }
+}
+(git -C "$flutterRoot" ls-tree --format "%(objectname) %(path)" $baseRef -- $trackedFiles | Out-String) -replace "`r`n", "`n"  | Out-File -NoNewline -Encoding ascii hash.txt
 git hash-object hash.txt
 Remove-Item hash.txt

bin/internal/content_aware_hash.sh

@@ -25,4 +25,24 @@ unset GIT_WORK_TREE
 # bin/internal/content_aware_hash.ps1: script for calculating the hash on windows
 # bin/internal/content_aware_hash.sh: script for calculating the hash on mac/linux
 # .github/workflows/content-aware-hash.yml: github action for CI/CD hashing
-git -C "$FLUTTER_ROOT" ls-tree --format "%(objectname) %(path)" HEAD DEPS engine bin/internal/release-candidate-branch.version | git hash-object --stdin
+TRACKEDFILES="DEPS engine bin/internal/release-candidate-branch.version"
+BASEREF="HEAD"
+
+set +e
+# We will fallback to origin/master if upstream is not detected.
+git -C "$FLUTTER_ROOT" remote get-url upstream >/dev/null 2>&1
+exit_code=$?
+set -e
+if [[ $exit_code -eq 0 ]]; then
+  MERGEBASE=$(git -C "$FLUTTER_ROOT" merge-base HEAD upstream/master)
+else
+  MERGEBASE=$(git -C "$FLUTTER_ROOT" merge-base HEAD origin/master)
+fi
+
+# Check to see if we're in a local development branch and the branch has any
+# changes to engine code - including non-committed changes.
+if [ "$(git -C "$FLUTTER_ROOT" rev-parse --abbrev-ref HEAD)" != "master" ] && \
+    ! git -C "$FLUTTER_ROOT" diff --quiet "$MERGEBASE" -- $TRACKEDFILES; then
+  BASEREF="$MERGEBASE"
+fi
+git -C "$FLUTTER_ROOT" ls-tree --format "%(objectname) %(path)" $BASEREF -- $TRACKEDFILES | git hash-object --stdin

dev/tools/test/content_aware_hash_test.dart

@@ -114,8 +114,21 @@ void main() {
     return run(executable, args);
   }
 
+  /// Sets up and fetches a [remote] (such as `upstream` or `origin`) for [testRoot.root].
+  ///
+  /// The remote points at itself (`testRoot.root.path`) for ease of testing.
+  void setupRemote({required String remote, String? rootPath}) {
+    run('git', <String>[
+      'remote',
+      'add',
+      remote,
+      rootPath ?? testRoot.root.path,
+    ], workingPath: rootPath);
+    run('git', <String>['fetch', remote], workingPath: rootPath);
+  }
+
   /// Initializes a blank git repo in [testRoot.root].
-  void initGitRepoWithBlankInitialCommit({String? workingPath}) {
+  void initGitRepoWithBlankInitialCommit({String? workingPath, String remote = 'upstream'}) {
     run('git', <String>['init', '--initial-branch', 'master'], workingPath: workingPath);
     // autocrlf is very important for tests to work on windows.
     run('git', 'config --local core.autocrlf true'.split(' '), workingPath: workingPath);
@@ -133,6 +146,8 @@ void main() {
       '-m',
       'Initial commit',
     ], workingPath: workingPath);
+
+    setupRemote(remote: remote, rootPath: workingPath);
   }
 
   void writeFileAndCommit(File file, String contents) {
@@ -141,11 +156,58 @@ void main() {
     run('git', <String>['commit', '--all', '-m', 'changed ${file.basename} to $contents']);
   }
 
+  void gitSwitchBranch(String branch, {bool create = true}) {
+    run('git', <String>['switch', if (create) '-c', branch]);
+  }
+
   test('generates a hash', () async {
     initGitRepoWithBlankInitialCommit();
     expect(runContentAwareHash(), processStdout('3bbeb6a394378478683ece4f8e8663c42f8dc814'));
   });
 
+  test('generates a hash for origin', () {
+    initGitRepoWithBlankInitialCommit(remote: 'origin');
+    expect(runContentAwareHash(), processStdout('3bbeb6a394378478683ece4f8e8663c42f8dc814'));
+  });
+
+  group('ignores local engine for', () {
+    test('upstream', () {
+      initGitRepoWithBlankInitialCommit();
+      gitSwitchBranch('engineTest');
+      testRoot.deps.writeAsStringSync('deps changed');
+      expect(
+        runContentAwareHash(),
+        processStdout('3bbeb6a394378478683ece4f8e8663c42f8dc814'),
+        reason: 'content hash from master for non-committed file',
+      );
+
+      writeFileAndCommit(testRoot.deps, 'deps changed');
+      expect(
+        runContentAwareHash(),
+        processStdout('3bbeb6a394378478683ece4f8e8663c42f8dc814'),
+        reason: 'content hash from master for committed file',
+      );
+    });
+
+    test('origin', () {
+      initGitRepoWithBlankInitialCommit(remote: 'origin');
+      gitSwitchBranch('engineTest');
+      testRoot.deps.writeAsStringSync('deps changed');
+      expect(
+        runContentAwareHash(),
+        processStdout('3bbeb6a394378478683ece4f8e8663c42f8dc814'),
+        reason: 'content hash from master for non-committed file',
+      );
+
+      writeFileAndCommit(testRoot.deps, 'deps changed');
+      expect(
+        runContentAwareHash(),
+        processStdout('3bbeb6a394378478683ece4f8e8663c42f8dc814'),
+        reason: 'content hash from master for committed file',
+      );
+    });
+  });
+
   group('generates a different hash when', () {
     setUp(() {
       initGitRepoWithBlankInitialCommit();