Make hash script for Frob (#157390)

All engine hashing is required to be version controlled, otherwise you'll be broken.

dev/bots/analyze.dart

@@ -2238,6 +2238,7 @@ const Set<String> kExecutableAllowlist = <String>{
 
   'dev/tools/gen_keycodes/bin/gen_keycodes',
   'dev/tools/repackage_gradle_wrapper.sh',
+  'dev/tools/bin/engine_hash.sh',
 
   'packages/flutter_tools/bin/macos_assemble.sh',
   'packages/flutter_tools/bin/tool_backend.sh',

dev/tools/bin/engine_hash.dart

@@ -2,6 +2,14 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+// ---------------------------------- NOTE ----------------------------------
+//
+// We must keep the logic in this file consistent with the logic in the
+// `engine_hash.sh` script in the same directory to ensure that Flutter
+// continues to work across all platforms!
+//
+// --------------------------------------------------------------------------
+
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
@@ -91,7 +99,7 @@ Future<String> engineHash(
         <String>[
           'git',
           'merge-base',
-          'upstream/main',
+          'upstream/master',
           'HEAD',
         ],
       );

dev/tools/bin/engine_hash.sh

@@ -0,0 +1,74 @@
+#!/usr/bin/env bash
+# Copyright 2014 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# ---------------------------------- NOTE ---------------------------------- #
+#
+# We must keep the logic in this file consistent with the logic in the
+# `engine_hash.dart` script in the same directory to ensure that Flutter
+# continues to work across all platforms!
+#
+# -------------------------------------------------------------------------- #
+
+# TODO(codefu): Add a test that this always outputs the same hash as
+# `engine_hash.dart` when the repositories are merged
+
+STRATEGY=head
+
+HELP=$(
+    cat <<EOF
+Calculate the hash signature for the Flutter Engine\n
+\t-s|--strategy\t<head,mergeBase>\n
+\t\tthead:      hash from git HEAD\n
+\t\tmergeBase: hash from the merge-base of HEAD and upstream/master\n
+EOF
+)
+
+function print_help() {
+    if [ "${1:-0}" -eq 0 ]; then
+        echo -e $HELP
+        exit 0
+    else
+        echo >&2 -e $HELP
+        exit $1
+    fi
+}
+
+while [[ "$#" -gt 0 ]]; do
+    case $1 in
+    -s | --strategy)
+        STRATEGY="$2"
+        shift # past argument
+        shift # past value
+        ;;
+    -h | --help)
+        print_help
+        ;;
+    -* | --*)
+        echo >&2 -e "Unknown option $1\n"
+        print_help 1
+        ;;
+    esac
+done
+
+BASE=HEAD
+case $STRATEGY in
+head) ;;
+mergeBase)
+    BASE=$(git merge-base upstream/master HEAD)
+    ;;
+*)
+    echo >&2 -e "Unknown strategy $1\n"
+    print_help 1
+    ;;
+esac
+
+LSTREE=$(git ls-tree -r $BASE engine DEPS)
+if [ ${#LSTREE} -eq 0 ]; then
+    echo >&2 Error calculating engine hash: Not in a monorepo
+    exit 1
+else
+    HASH=$(echo "$LSTREE" | sha1sum | head -c 40)
+    echo $HASH
+fi

dev/tools/test/engine_hash_test.dart

@@ -16,7 +16,7 @@ void main() {
       (
         exe: 'git',
         command: 'merge-base',
-        rest: <String>['upstream/main', 'HEAD'],
+        rest: <String>['upstream/master', 'HEAD'],
         exitCode: 0,
         stdout: 'abcdef1234',
         stderr: null