script for fetching correct flutter version

.cirrus.yml

@@ -11,10 +11,9 @@ web_shard_template: &WEB_SHARD_TEMPLATE
     ./flutter/tools/gn --unoptimized --full-dart-sdk
     ninja -C out/host_debug_unopt
   fetch_framework_script: |
-    mkdir -p $FRAMEWORK_PATH
-    cd $FRAMEWORK_PATH
-    git clone https://github.com/flutter/flutter.git
-    cd flutter
+    cd $ENGINE_PATH/src/flutter/tools
+    ./clone_flutter.sh
+    cd $FRAMEWORK_PATH/flutter
     bin/flutter update-packages --local-engine=host_debug_unopt
   script:
     - dart --enable-asserts $FRAMEWORK_PATH/flutter/dev/bots/test.dart --local-engine=host_debug_unopt

tools/clone_flutter.sh

@@ -0,0 +1,64 @@
+#!/bin/bash
+set -e
+set -x
+
+if [[ "$CIRRUS_CI" = false || -z $CIRRUS_CI ]]
+then
+  echo "This script is aimed to be run on CI environments. Do not run locally."
+  exit 1
+fi
+
+if [[ -z $ENGINE_PATH ]]
+then
+  echo "Engine path should be set to run the script."
+  exit 1
+fi
+
+# Go to the engine git repo to get the date of the latest commit.
+cd $ENGINE_PATH/src/flutter
+
+# Special handling of release branches.
+ENGINE_BRANCH_NAME=`git branch | grep '*' | cut -d ' ' -f2`
+versionregex="^v[[:digit:]]+\."
+ON_RELEASE_BRANCH=false
+echo "Engine on branch $ENGINE_BRANCH_NAME"
+if [[ $ENGINE_BRANCH_NAME =~ $versionregex ]]
+then
+  echo "release branch $ENGINE_BRANCH_NAME"
+  ON_RELEASE_BRANCH=true
+fi
+
+# Get latest commit's time for the engine repo.
+# Use date based on local time otherwise timezones might get mixed.
+LATEST_COMMIT_TIME_ENGINE=`git log -1 --date=local --format="%ad"`
+echo "Latest commit time on engine found as $LATEST_COMMIT_TIME_ENGINE"
+
+# Do rest of the task in the root directory
+cd ~
+mkdir -p $FRAMEWORK_PATH
+cd $FRAMEWORK_PATH
+# Clone the Flutter Framework.
+git clone https://github.com/flutter/flutter.git
+cd flutter
+
+FRAMEWORK_BRANCH_NAME=`git branch | grep '*' | cut -d ' ' -f2`
+if [[ "$ON_RELEASE_BRANCH" = true && ENGINE_BRANCH_NAME != FRAMEWORK_BRANCH_NAME ]]
+then
+  echo "For a release framework and engine should be on the same version."
+  echo "Switching branches on Framework to from $FRAMEWORK_BRANCH_NAME to $ENGINE_BRANCH_NAME"
+  # Switch to the same version branch with the engine.
+  # If same version branch does not exits, fail.
+  SWITCH_RESULT=`git checkout $ENGINE_BRANCH_NAME` || true
+  if [[ -z "$SWITCH_RESULT" ]]
+  then
+    echo "$ENGINE_BRANCH_NAME Branch not found on framework. Quit."
+    exit 1
+  fi
+fi
+
+# Get the time of the youngest commit older than engine commit.
+# Git log uses commit date not the author date.
+# Before makes the comparison considering the timezone as well.
+COMMIT_NO=`git log --before="$LATEST_COMMIT_TIME_ENGINE" -n 1 | grep commit | cut -d ' ' -f2`
+echo "Using the flutter/flutter commit $COMMIT_NO";
+git reset --hard $COMMIT_NO