diff --git a/.cirrus.yml b/.cirrus.yml
index 16e84e60f2..b7b1062d04 100644
--- a/.cirrus.yml
+++ b/.cirrus.yml
@@ -4,7 +4,7 @@
 # YAML anchors used to share fields between tasks.
 # See https://confluence.atlassian.com/bitbucket/yaml-anchors-960154027.html
 web_shard_template: &WEB_SHARD_TEMPLATE
-  only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'packages/flutter_web_plugins/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+  only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'packages/flutter_web_plugins/**', 'bin/**') || $CIRRUS_PR == ''"
   environment:
     # As of March 2020, the Web shards needed 16G of RAM and 4 CPUs to run all framework tests with goldens without flaking.
     WEB_SHARD_COUNT: 8
@@ -24,12 +24,12 @@ linux_shard_template: &LINUX_SHARD_TEMPLATE
     - dart --enable-asserts ./dev/bots/test.dart
 
 windows_shard_template: &WINDOWS_SHARD_TEMPLATE
-  only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/internal/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41941
+  only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41941
   script:
     - dart --enable-asserts ./dev/bots/test.dart
 
 macos_shard_template: &MACOS_SHARD_TEMPLATE
-  only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/internal/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41941
+  only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41941
   script:
     - ulimit -S -n 2048 # https://github.com/flutter/flutter/issues/2976
     - dart --enable-asserts ./dev/bots/test.dart
@@ -127,7 +127,7 @@ task:
         - flutter precache --flutter_runner --no-android --no-ios
 
     - name: framework_tests-widgets-linux
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # We use 3 CPUs because that's the minimum required to get framework_tests-widgets-linux
         # running fast enough that it is not the long pole, as of October 2019.
@@ -137,7 +137,7 @@ task:
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: framework_tests-libraries-linux
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # We use 3 CPUs because that's the minimum required to get the
         # framework_tests-libraries-linux shard running fast enough that it is not the long pole, as
@@ -149,7 +149,7 @@ task:
 
     - name: framework_tests-misc-linux
       # this includes the tests for directories in dev/
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_goldens/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_goldens/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # We use 3 CPUs because that's the minimum required to get framework_tests-misc-linux
         # running fast enough that it is not the long pole, as of October 2019.
@@ -158,7 +158,7 @@ task:
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: tool_tests-general-linux
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of November 2019, the tool_tests-general-linux shard got faster with more CPUs up to 4
         # CPUs, and needed at least 10G of RAM to not run out of memory.
@@ -168,7 +168,7 @@ task:
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: tool_tests-commands-linux
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of October 2019, the tool_tests-commands-linux shard got faster with more CPUs up to 6
         # CPUs, and needed at least 8G of RAM to not run out of memory.
@@ -179,7 +179,7 @@ task:
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: tool_tests-integration-linux
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of October 2019, the tool_tests-integration-linux shard got faster with more CPUs up to
         # 6 CPUs, and needed at least 8G of RAM to not run out of memory.
@@ -202,7 +202,7 @@ task:
         - bash <(curl -s https://codecov.io/bash) -c -f packages/flutter_tools/coverage/lcov.info -F flutter_tool
 
     - name: web_integration_tests
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/**', 'packages/flutter_web_plugins/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/**', 'packages/flutter_web_plugins/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of October 2019, the Web shards needed more than 6G of RAM.
         CPU: 2
@@ -271,7 +271,7 @@ task:
     # TODO(ianh): name: add_to_app_tests-linux
 
     - name: docs-linux # linux-only
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_drive/**', 'packages/flutter_localizations/**', 'packages/flutter_goldens/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_drive/**', 'packages/flutter_localizations/**', 'packages/flutter_goldens/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # Empirically, as of October 2019, the docs-linux shard took about 30 minutes when run with
         # 1 CPU and 4G of RAM. 2 CPUs reduced that to 20 minutes, more CPUs did not improve matters.
@@ -303,7 +303,7 @@ task:
       <<: *FIREBASE_SHARD_TEMPLATE
 
     - name: web_smoke_test
-      only_if: "changesInclude('.cirrus.yml', 'examples/hello_world/**' ,'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'packages/flutter_web_plugins/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'examples/hello_world/**' ,'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'packages/flutter_web_plugins/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # Tests Hello World with Flutter Web Engine using Flutter Driver. Should not need more resources.
         CPU: 2
@@ -370,7 +370,7 @@ task:
     - git fetch origin master
   matrix:
     - name: framework_tests-widgets-windows
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of December 2019, framework_tests-widgets-windows needs 4 CPUs to pass reliably.
         # With a min of 4 CPUs and 4 GB of RAM, it ran in about 50 minutes. Increasing to 8 CPUs and
@@ -385,7 +385,7 @@ task:
         - dart --enable-asserts dev\bots\test.dart
 
     - name: framework_tests-libraries-windows
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of December 2019, the framework_tests-libraries-windows shard needed 2 CPUs to pass.
         # With a min of 2 CPUs and 2 GB RAM, it ran in about 60 minutes. Increasing to 8 CPUs made
@@ -401,7 +401,7 @@ task:
 
     - name: framework_tests-misc-windows
       # this includes the tests for directories in dev/
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_goldens/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_goldens/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of December 2019, the framework_tests-misc-windows shard needed 2 CPUs and 3 GB RAM
         # to pass (taking ~40 minutes). Increasing to 4 CPUs (necessitating 4 GB RAM per Cirrus)
@@ -412,7 +412,7 @@ task:
         - dart --enable-asserts dev\bots\test.dart
 
     - name: tool_tests-general-windows
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of December 2019, the tool_tests-general-windows shard required 2 CPUs and 8 GB RAM to
         # pass. Raising that to 4 CPUs sped it up to ~30 minutes, with further provisioning yielding
@@ -423,7 +423,7 @@ task:
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: tool_tests-commands-windows
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of December 2019, the tool_tests-commands-windows shard needed 4 CPUs and 8 GB RAM to
         # reliably pass and not be the long pole, running in about 25 minutes. Bumping beyond these
@@ -434,7 +434,7 @@ task:
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: tool_tests-integration-windows
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         # As of December 2019, the tool_tests-integration-windows shard required 6 GB RAM to pass.
         # Emperically, 4 CPUs and 10 GB RAM yielded optimal results (~22 minutes); bumping beyond
@@ -447,7 +447,7 @@ task:
     # TODO(ianh): Enable Web tests on Windows
 
     - name: build_tests-0-windows
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/internal/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41941
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41941
       environment:
         # As of December 2019, the build_tests-windows shard requires 6 GB RAM to pass.
         # Emperically, using 6 CPUs and 10 GB RAM yielded optimal results (~33 minutes);
@@ -458,7 +458,7 @@ task:
         - dart --enable-asserts dev\bots\test.dart
 
     - name: build_tests-1_last-windows
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/internal/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41941
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41941
       environment:
         # As of December 2019, the build_tests-windows shard requires 6 GB RAM to pass.
         # Emperically, using 6 CPUs and 10 GB RAM yielded optimal results (~33 minutes);
@@ -552,7 +552,7 @@ task:
       - which flutter
   matrix:
     - name: framework_tests-widgets-macos
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         GOLDCTL: "$CIRRUS_WORKING_DIR/depot_tools/goldctl"
         GOLD_SERVICE_ACCOUNT: ENCRYPTED[3afeea5ac7201151c3d0dc9648862f0462b5e4f55dc600ca8b692319622f7c3eda3d577b1b16cc2ef0311b7314c1c095]
@@ -562,7 +562,7 @@ task:
         - dart --enable-asserts dev/bots/test.dart
 
     - name: framework_tests-libraries-macos
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       environment:
         GOLDCTL: "$CIRRUS_WORKING_DIR/depot_tools/goldctl"
         GOLD_SERVICE_ACCOUNT: ENCRYPTED[3afeea5ac7201151c3d0dc9648862f0462b5e4f55dc600ca8b692319622f7c3eda3d577b1b16cc2ef0311b7314c1c095]
@@ -573,25 +573,25 @@ task:
 
     - name: framework_tests-misc-macos
       # this includes the tests for directories in dev/
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_goldens/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter/**', 'packages/flutter_goldens/**', 'packages/flutter_test/**', 'packages/flutter_tools/lib/src/test/**', 'bin/**') || $CIRRUS_PR == ''"
       script:
         - ulimit -S -n 2048 # https://github.com/flutter/flutter/issues/2976
         - dart --enable-asserts dev/bots/test.dart
 
     - name: tool_tests-general-macos
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       script:
         - ulimit -S -n 2048 # https://github.com/flutter/flutter/issues/2976
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: tool_tests-commands-macos
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       script:
         - ulimit -S -n 2048 # https://github.com/flutter/flutter/issues/2976
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: tool_tests-integration-macos
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/internal/**') || $CIRRUS_PR == ''"
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'packages/flutter_tools/**', 'bin/**') || $CIRRUS_PR == ''"
       script:
         - ulimit -S -n 2048 # https://github.com/flutter/flutter/issues/2976
         - dart --enable-asserts ./dev/bots/test.dart
@@ -599,12 +599,12 @@ task:
     # TODO(ianh): Enable Web tests on macOS.
 
     - name: build_tests-0-macos
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/internal/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41940
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41940
       script:
         - dart --enable-asserts ./dev/bots/test.dart
 
     - name: build_tests-1_last-macos
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/internal/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41940
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41940
       script:
         - dart --enable-asserts ./dev/bots/test.dart
 
@@ -621,7 +621,7 @@ task:
       << : *MACOS_SHARD_TEMPLATE
 
     - name: add_to_app_tests-macos
-      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/internal/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41940
+      only_if: "changesInclude('.cirrus.yml', 'dev/**', 'bin/**') || $CIRRUS_PR == ''" # https://github.com/flutter/flutter/issues/41940
       skip: true # https://github.com/flutter/flutter/pull/42444
       script:
         - ulimit -S -n 2048 # https://github.com/flutter/flutter/issues/2976
diff --git a/bin/dart b/bin/dart
new file mode 100755
index 0000000000..a2d317f79c
--- /dev/null
+++ b/bin/dart
@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+# Copyright 2014 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+# ---------------------------------- NOTE ---------------------------------- #
+#
+# Please keep the logic in this file consistent with the logic in the
+# `dart.bat` script in the same directory to ensure that Flutter & Dart continue
+# to work across all platforms!
+#
+# -------------------------------------------------------------------------- #
+
+set -e
+
+unset CDPATH
+
+function follow_links() {
+  cd -P "${1%/*}"
+  local file="$PWD/${1##*/}"
+  while [[ -h "$file" ]]; do
+    # On Mac OS, readlink -f doesn't work.
+    cd -P "${file%/*}"
+    file="$(readlink "$file")"
+    cd -P "${file%/*}"
+    file="$PWD/${file##*/}"
+  done
+  echo "$PWD/${file##*/}"
+}
+
+# Convert a filesystem path to a format usable by Dart's URI parser.
+function path_uri() {
+  # Reduce multiple leading slashes to a single slash.
+  echo "$1" | sed -E -e "s,^/+,/,"
+}
+
+PROG_NAME="$(path_uri "$(follow_links "$BASH_SOURCE")")"
+BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
+
+# To define `shared::execute()` function
+source "$BIN_DIR/shared.sh"
+
+shared::execute "$@"
diff --git a/bin/dart.bat b/bin/dart.bat
new file mode 100644
index 0000000000..4927aaefa7
--- /dev/null
+++ b/bin/dart.bat
@@ -0,0 +1,37 @@
+@ECHO off
+REM Copyright 2014 The Flutter Authors. All rights reserved.
+REM Use of this source code is governed by a BSD-style license that can be
+REM found in the LICENSE file.
+
+REM ---------------------------------- NOTE ----------------------------------
+REM
+REM Please keep the logic in this file consistent with the logic in the
+REM `dart` script in the same directory to ensure that Flutter & Dart continue to
+REM work across all platforms!
+REM
+REM --------------------------------------------------------------------------
+
+SETLOCAL ENABLEDELAYEDEXPANSION
+
+FOR %%i IN ("%~dp0..") DO SET FLUTTER_ROOT=%%~fi
+
+REM Include shared scripts in shared.bat
+SET shared_bin=%FLUTTER_ROOT%/bin/internal/shared.bat
+CALL "%shared_bin%"
+
+SET cache_dir=%FLUTTER_ROOT%\bin\cache
+SET dart_sdk_path=%cache_dir%\dart-sdk
+SET dart=%dart_sdk_path%\bin\dart.exe
+
+REM Chaining the call to 'dart' and 'exit' with an ampersand ensures that
+REM Windows reads both commands into memory once before executing them. This
+REM avoids nasty errors that may otherwise occur when the dart command (e.g. as
+REM part of 'flutter upgrade') modifies this batch script while it is executing.
+REM
+REM Do not use the CALL command in the next line to execute Dart. CALL causes
+REM Windows to re-read the line from disk after the CALL command has finished
+REM regardless of the ampersand chain.
+"%dart%" %* & exit /B !ERRORLEVEL!
+
+:final_exit
+EXIT /B %exit_code%
diff --git a/bin/flutter b/bin/flutter
index 87bd597110..89ec060c89 100755
--- a/bin/flutter
+++ b/bin/flutter
@@ -3,7 +3,6 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-
 # ---------------------------------- NOTE ---------------------------------- #
 #
 # Please keep the logic in this file consistent with the logic in the
@@ -35,158 +34,10 @@ function path_uri() {
   echo "$1" | sed -E -e "s,^/+,/,"
 }
 
-function _rmlock () {
-  [ -n "$FLUTTER_UPGRADE_LOCK" ] && rm -f "$FLUTTER_UPGRADE_LOCK"
-}
-
-function retry_upgrade {
-  local total_tries="10"
-  local remaining_tries=$((total_tries - 1))
-  while [[ "$remaining_tries" -gt 0 ]]; do
-    (cd "$FLUTTER_TOOLS_DIR" && "$PUB" upgrade "$VERBOSITY" --no-precompile) && break
-    echo "Error: Unable to 'pub upgrade' flutter tool. Retrying in five seconds... ($remaining_tries tries left)"
-    remaining_tries=$((remaining_tries - 1))
-    sleep 5
-  done
-
-  if [[ "$remaining_tries" == 0 ]]; then
-    echo "Command 'pub upgrade' still failed after $total_tries tries, giving up."
-    return 1
-  fi
-  return 0
-}
-
-function upgrade_flutter () {
-  mkdir -p "$FLUTTER_ROOT/bin/cache"
-
-  # This function is executed with a redirect that pipes the source of
-  # this script into file descriptor 3.
-  #
-  # To ensure that we don't simultaneously update Dart in multiple
-  # parallel instances, we try to obtain an exclusive lock on this
-  # file descriptor (and thus this script's source file) while we are
-  # updating Dart and compiling the script. To do this, we try to use
-  # the command line program "flock", which is available on many
-  # Unix-like platforms, in particular on most Linux distributions.
-  # You give it a file descriptor, and it locks the corresponding
-  # file, having inherited the file descriptor from the shell.
-  #
-  # Complicating matters, there are two major scenarios where this
-  # will not work.
-  #
-  # The first is if the platform doesn't have "flock", for example on Mac.
-  # There is not a direct equivalent, so on platforms that don't have flock,
-  # we fall back to using a lockfile and spinlock with "shlock".  This
-  # doesn't work as well over NFS as it relies on PIDs. Any platform
-  # without either of these tools has no locking at all. To determine if we
-  # have "flock" or "shlock" available, we abuse the "hash" shell built-in.
-  #
-  # The second complication is NFS. On NFS, to obtain an exclusive
-  # lock you need a file descriptor that is open for writing, because
-  # NFS implements exclusive locks by writing, or some such. Thus, we
-  # ignore errors from flock. We do so by using the '|| true' trick,
-  # since we are running in a 'set -e' environment wherein all errors
-  # are fatal, and by redirecting all output to /dev/null, since
-  # users will typically not care about errors from flock and are
-  # more likely to be confused by them than helped.
-  #
-  # For "flock", the lock is released when the file descriptor goes out of
-  # scope,  i.e. when this function returns.  The lock is released via
-  # a trap when using "shlock".
-  if hash flock 2>/dev/null; then
-    flock 3 2>/dev/null || true
-  elif hash shlock 2>/dev/null; then
-    FLUTTER_UPGRADE_LOCK="$FLUTTER_ROOT/bin/cache/.upgrade_lock"
-    while ! shlock -f "$FLUTTER_UPGRADE_LOCK" -p $$ ; do sleep .1 ; done
-    trap _rmlock EXIT
-  fi
-
-  local revision="$(cd "$FLUTTER_ROOT"; git rev-parse HEAD)"
-
-  # Invalidate cache if:
-  #  * SNAPSHOT_PATH is not a file, or
-  #  * STAMP_PATH is not a file with nonzero size, or
-  #  * Contents of STAMP_PATH is not our local git HEAD revision, or
-  #  * pubspec.yaml last modified after pubspec.lock
-  if [[ ! -f "$SNAPSHOT_PATH" || ! -s "$STAMP_PATH" || "$(cat "$STAMP_PATH")" != "$revision" || "$FLUTTER_TOOLS_DIR/pubspec.yaml" -nt "$FLUTTER_TOOLS_DIR/pubspec.lock" ]]; then
-    rm -f "$FLUTTER_ROOT/version"
-    touch "$FLUTTER_ROOT/bin/cache/.dartignore"
-    "$FLUTTER_ROOT/bin/internal/update_dart_sdk.sh"
-    VERBOSITY="--verbosity=error"
-
-    echo Building flutter tool...
-    if [[ "$CI" == "true" || "$BOT" == "true" || "$CONTINUOUS_INTEGRATION" == "true" || "$CHROME_HEADLESS" == "1" ]]; then
-      PUB_ENVIRONMENT="$PUB_ENVIRONMENT:flutter_bot"
-      VERBOSITY="--verbosity=normal"
-    fi
-    export PUB_ENVIRONMENT="$PUB_ENVIRONMENT:flutter_install"
-
-    if [[ -d "$FLUTTER_ROOT/.pub-cache" ]]; then
-      export PUB_CACHE="${PUB_CACHE:-"$FLUTTER_ROOT/.pub-cache"}"
-    fi
-
-    retry_upgrade
-
-    "$DART" --disable-dart-dev $FLUTTER_TOOL_ARGS --snapshot="$SNAPSHOT_PATH" --packages="$FLUTTER_TOOLS_DIR/.packages" --no-enable-mirrors "$SCRIPT_PATH"
-    echo "$revision" > "$STAMP_PATH"
-  fi
-  # The exit here is duplicitous since the function is run in a subshell,
-  # but this serves as documentation that running the function in a
-  # subshell is required to make sure any lockfile created by shlock
-  # is cleaned up.
-  exit $?
-}
-
 PROG_NAME="$(path_uri "$(follow_links "$BASH_SOURCE")")"
 BIN_DIR="$(cd "${PROG_NAME%/*}" ; pwd -P)"
-export FLUTTER_ROOT="$(cd "${BIN_DIR}/.." ; pwd -P)"
 
-FLUTTER_TOOLS_DIR="$FLUTTER_ROOT/packages/flutter_tools"
-SNAPSHOT_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.snapshot"
-STAMP_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.stamp"
-SCRIPT_PATH="$FLUTTER_TOOLS_DIR/bin/flutter_tools.dart"
-DART_SDK_PATH="$FLUTTER_ROOT/bin/cache/dart-sdk"
+# To define `shared::execute()` function
+source "$BIN_DIR/shared.sh"
 
-DART="$DART_SDK_PATH/bin/dart"
-PUB="$DART_SDK_PATH/bin/pub"
-
-# If running over git-bash, overrides the default UNIX
-# executables with win32 executables
-case "$(uname -s)" in
-  MINGW32*)
-    DART="$DART.exe"
-    PUB="$PUB.bat"
-    ;;
-esac
-
-# Test if running as superuser – but don't warn if running within Docker
-if [[ "$EUID" == "0" && ! -f /.dockerenv ]]; then
-  echo "   Woah! You appear to be trying to run flutter as root."
-  echo "   We strongly recommend running the flutter tool without superuser privileges."
-  echo "  /"
-  echo "📎"
-fi
-
-# Test if Git is available on the Host
-if ! hash git 2>/dev/null; then
-  echo "Error: Unable to find git in your PATH."
-  exit 1
-fi
-# Test if the flutter directory is a git clone (otherwise git rev-parse HEAD would fail)
-if [[ ! -e "$FLUTTER_ROOT/.git" ]]; then
-  echo "Error: The Flutter directory is not a clone of the GitHub project."
-  echo "       The flutter tool requires Git in order to operate properly;"
-  echo "       to set up Flutter, run the following command:"
-  echo "       git clone -b stable https://github.com/flutter/flutter.git"
-  exit 1
-fi
-
-# To debug the tool, you can uncomment the following lines to enable checked mode and set an observatory port:
-# FLUTTER_TOOL_ARGS="--enable-asserts $FLUTTER_TOOL_ARGS"
-# FLUTTER_TOOL_ARGS="$FLUTTER_TOOL_ARGS --observe=65432"
-
-(upgrade_flutter) 3< "$PROG_NAME"
-
-# FLUTTER_TOOL_ARGS isn't quoted below, because it is meant to be considered as
-# separate space-separated args.
-"$DART" --disable-dart-dev --packages="$FLUTTER_TOOLS_DIR/.packages" $FLUTTER_TOOL_ARGS "$SNAPSHOT_PATH" "$@"
+shared::execute "$@"
diff --git a/bin/flutter.bat b/bin/flutter.bat
index d118e80d99..36b96fd0f8 100644
--- a/bin/flutter.bat
+++ b/bin/flutter.bat
@@ -6,7 +6,7 @@ REM found in the LICENSE file.
 REM ---------------------------------- NOTE ----------------------------------
 REM
 REM Please keep the logic in this file consistent with the logic in the
-REM `flutter` script in the same directory to ensure that Flutter continues to
+REM `flutter` script in the same directory to ensure that Flutter & Dart continue to
 REM work across all platforms!
 REM
 REM --------------------------------------------------------------------------
@@ -15,171 +15,18 @@ SETLOCAL ENABLEDELAYEDEXPANSION
 
 FOR %%i IN ("%~dp0..") DO SET FLUTTER_ROOT=%%~fi
 
+REM Include shared scripts in shared.bat
+SET shared_bin=%FLUTTER_ROOT%/bin/internal/shared.bat
+CALL "%shared_bin%"
+
 SET flutter_tools_dir=%FLUTTER_ROOT%\packages\flutter_tools
 SET cache_dir=%FLUTTER_ROOT%\bin\cache
 SET snapshot_path=%cache_dir%\flutter_tools.snapshot
-SET stamp_path=%cache_dir%\flutter_tools.stamp
-SET script_path=%flutter_tools_dir%\bin\flutter_tools.dart
 SET dart_sdk_path=%cache_dir%\dart-sdk
-SET engine_stamp=%cache_dir%\engine-dart-sdk.stamp
-SET engine_version_path=%FLUTTER_ROOT%\bin\internal\engine.version
-SET pub_cache_path=%FLUTTER_ROOT%\.pub-cache
-
 SET dart=%dart_sdk_path%\bin\dart.exe
-SET pub=%dart_sdk_path%\bin\pub.bat
-
-REM If available, add location of bundled mingit to PATH
-SET mingit_path=%FLUTTER_ROOT%\bin\mingit\cmd
-IF EXIST "%mingit_path%" SET PATH=%PATH%;%mingit_path%
-
-REM Test if Git is available on the Host
-where /q git || ECHO Error: Unable to find git in your PATH. && EXIT /B 1
-REM  Test if the flutter directory is a git clone, otherwise git rev-parse HEAD would fail
-IF NOT EXIST "%flutter_root%\.git" (
-  ECHO Error: The Flutter directory is not a clone of the GitHub project.
-  ECHO        The flutter tool requires Git in order to operate properly;
-  ECHO        to set up Flutter, run the following command:
-  ECHO        git clone -b stable https://github.com/flutter/flutter.git
-  EXIT /B 1
-)
-
-REM Detect which PowerShell executable is available on the Host
-REM PowerShell version <= 5: PowerShell.exe
-REM PowerShell version >= 6: pwsh.exe
-WHERE /Q pwsh.exe && (
-    SET powershell_executable=pwsh.exe
-) || WHERE /Q PowerShell.exe && (
-    SET powershell_executable=PowerShell.exe
-) || (
-    ECHO Error: PowerShell executable not found.
-    ECHO        Either pwsh.exe or PowerShell.exe must be in your PATH.
-    EXIT /B 1
-)
-
-REM Ensure that bin/cache exists.
-IF NOT EXIST "%cache_dir%" MKDIR "%cache_dir%"
-
-REM If the cache still doesn't exist, fail with an error that we probably don't have permissions.
-IF NOT EXIST "%cache_dir%" (
-  ECHO Error: Unable to create cache directory at
-  ECHO            %cache_dir%
-  ECHO.
-  ECHO        This may be because flutter doesn't have write permissions for
-  ECHO        this path. Try moving the flutter directory to a writable location,
-  ECHO        such as within your home directory.
-  EXIT /B 1
-)
-
 
 REM To debug the tool, you can uncomment the following lines to enable checked mode and set an observatory port:
 REM SET FLUTTER_TOOL_ARGS="--enable-asserts %FLUTTER_TOOL_ARGS%"
-REM SET FLUTTER_TOOL_ARGS="%FLUTTER_TOOL_ARGS% --observe=65432"
-
-:acquire_lock
-2>NUL (
-  REM "3" is now stderr because of "2>NUL".
-  CALL :subroutine %* 2>&3 9> "%cache_dir%\flutter.bat.lock" || GOTO acquire_lock
-)
-GOTO :after_subroutine
-
-:subroutine
-  PUSHD "%flutter_root%"
-  FOR /f %%r IN ('git rev-parse HEAD') DO SET revision=%%r
-  POPD
-
-  REM The following IF conditions are all linked with a logical OR. However,
-  REM there is no OR operator in batch and a GOTO construct is used as replacement.
-
-  IF NOT EXIST "%engine_stamp%" GOTO do_sdk_update_and_snapshot
-  SET /P dart_required_version=<"%engine_version_path%"
-  SET /P dart_installed_version=<"%engine_stamp%"
-  IF !dart_required_version! NEQ !dart_installed_version! GOTO do_sdk_update_and_snapshot
-  IF NOT EXIST "%snapshot_path%" GOTO do_snapshot
-  IF NOT EXIST "%stamp_path%" GOTO do_snapshot
-  SET /P stamp_value=<"%stamp_path%"
-  IF !stamp_value! NEQ !revision! GOTO do_snapshot
-  SET pubspec_yaml_path=%flutter_tools_dir%\pubspec.yaml
-  SET pubspec_lock_path=%flutter_tools_dir%\pubspec.lock
-  FOR /F %%i IN ('DIR /B /O:D "%pubspec_yaml_path%" "%pubspec_lock_path%"') DO SET newer_file=%%i
-  FOR %%i IN (%pubspec_yaml_path%) DO SET pubspec_yaml_timestamp=%%~ti
-  FOR %%i IN (%pubspec_lock_path%) DO SET pubspec_lock_timestamp=%%~ti
-  IF "%pubspec_yaml_timestamp%" == "%pubspec_lock_timestamp%" SET newer_file=""
-  IF "%newer_file%" EQU "pubspec.yaml" GOTO do_snapshot
-
-  REM Everything is up-to-date - exit subroutine
-  EXIT /B
-
-  :do_sdk_update_and_snapshot
-    ECHO Checking Dart SDK version...
-    SET update_dart_bin=%FLUTTER_ROOT%/bin/internal/update_dart_sdk.ps1
-    REM Escape apostrophes from the executable path
-    SET "update_dart_bin=!update_dart_bin:'=''!"
-    %powershell_executable% -ExecutionPolicy Bypass -Command "Unblock-File -Path '%update_dart_bin%'; & '%update_dart_bin%'"
-    IF "%ERRORLEVEL%" NEQ "0" (
-      ECHO Error: Unable to update Dart SDK. Retrying...
-      timeout /t 5 /nobreak
-      GOTO :do_sdk_update_and_snapshot
-    )
-
-  :do_snapshot
-    IF EXIST "%FLUTTER_ROOT%\version" DEL "%FLUTTER_ROOT%\version"
-    ECHO: > "%cache_dir%\.dartignore"
-    ECHO Building flutter tool...
-    PUSHD "%flutter_tools_dir%"
-
-    REM Makes changes to PUB_ENVIRONMENT only visible to commands within SETLOCAL/ENDLOCAL
-    SETLOCAL
-      SET VERBOSITY=--verbosity=error
-      IF "%CI%" == "true" GOTO on_bot
-      IF "%BOT%" == "true" GOTO on_bot
-      IF "%CONTINUOUS_INTEGRATION%" == "true" GOTO on_bot
-      IF "%CHROME_HEADLESS%" == "1" GOTO on_bot
-      GOTO not_on_bot
-      :on_bot
-        SET PUB_ENVIRONMENT=%PUB_ENVIRONMENT%:flutter_bot
-        SET VERBOSITY=--verbosity=normal
-      :not_on_bot
-      SET PUB_ENVIRONMENT=%PUB_ENVIRONMENT%:flutter_install
-      IF "%PUB_CACHE%" == "" (
-        IF EXIST "%pub_cache_path%" SET PUB_CACHE=%pub_cache_path%
-      )
-
-      SET /A total_tries=10
-      SET /A remaining_tries=%total_tries%-1
-      :retry_pub_upgrade
-        ECHO Running pub upgrade...
-        CALL "%pub%" upgrade "%VERBOSITY%" --no-precompile
-        IF "%ERRORLEVEL%" EQU "0" goto :upgrade_succeeded
-        ECHO Error (%ERRORLEVEL%): Unable to 'pub upgrade' flutter tool. Retrying in five seconds... (%remaining_tries% tries left)
-        timeout /t 5 /nobreak 2>NUL
-        SET /A remaining_tries-=1
-        IF "%remaining_tries%" EQU "0" GOTO upgrade_retries_exhausted
-        GOTO :retry_pub_upgrade
-      :upgrade_retries_exhausted
-        SET exit_code=%ERRORLEVEL%
-        ECHO Error: 'pub upgrade' still failing after %total_tries% tries, giving up.
-        GOTO final_exit
-      :upgrade_succeeded
-    ENDLOCAL
-
-    POPD
-
-    IF "%FLUTTER_TOOL_ARGS%" == "" (
-      "%dart%" --disable-dart-dev --snapshot="%snapshot_path%" --packages="%flutter_tools_dir%\.packages" --no-enable-mirrors "%script_path%"
-    ) else (
-      "%dart%" --disable-dart-dev "%FLUTTER_TOOL_ARGS%" --snapshot="%snapshot_path%" --packages="%flutter_tools_dir%\.packages" "%script_path%"
-    )
-    IF "%ERRORLEVEL%" NEQ "0" (
-      ECHO Error: Unable to create dart snapshot for flutter tool.
-      SET exit_code=%ERRORLEVEL%
-      GOTO :final_exit
-    )
-    >"%stamp_path%" ECHO %revision%
-
-  REM Exit Subroutine
-  EXIT /B
-
-:after_subroutine
 
 REM Chaining the call to 'dart' and 'exit' with an ampersand ensures that
 REM Windows reads both commands into memory once before executing them. This
diff --git a/bin/internal/shared.bat b/bin/internal/shared.bat
new file mode 100644
index 0000000000..cd95979065
--- /dev/null
+++ b/bin/internal/shared.bat
@@ -0,0 +1,175 @@
+@ECHO off
+REM Copyright 2014 The Flutter Authors. All rights reserved.
+REM Use of this source code is governed by a BSD-style license that can be
+REM found in the LICENSE file.
+
+REM ---------------------------------- NOTE ----------------------------------
+REM
+REM Please keep the logic in this file consistent with the logic in the
+REM `shared.sh` script in the same directory to ensure that Flutter & Dart continue to
+REM work across all platforms!
+REM
+REM --------------------------------------------------------------------------
+
+SETLOCAL ENABLEDELAYEDEXPANSION
+
+SET flutter_tools_dir=%FLUTTER_ROOT%\packages\flutter_tools
+SET cache_dir=%FLUTTER_ROOT%\bin\cache
+SET snapshot_path=%cache_dir%\flutter_tools.snapshot
+SET stamp_path=%cache_dir%\flutter_tools.stamp
+SET script_path=%flutter_tools_dir%\bin\flutter_tools.dart
+SET dart_sdk_path=%cache_dir%\dart-sdk
+SET engine_stamp=%cache_dir%\engine-dart-sdk.stamp
+SET engine_version_path=%FLUTTER_ROOT%\bin\internal\engine.version
+SET pub_cache_path=%FLUTTER_ROOT%\.pub-cache
+
+SET dart=%dart_sdk_path%\bin\dart.exe
+SET pub=%dart_sdk_path%\bin\pub.bat
+
+REM If available, add location of bundled mingit to PATH
+SET mingit_path=%FLUTTER_ROOT%\bin\mingit\cmd
+IF EXIST "%mingit_path%" SET PATH=%PATH%;%mingit_path%
+
+REM Test if Git is available on the Host
+where /q git || ECHO Error: Unable to find git in your PATH. && EXIT /B 1
+REM  Test if the flutter directory is a git clone, otherwise git rev-parse HEAD would fail
+IF NOT EXIST "%flutter_root%\.git" (
+  ECHO Error: The Flutter directory is not a clone of the GitHub project.
+  ECHO        The flutter tool requires Git in order to operate properly;
+  ECHO        to set up Flutter, run the following command:
+  ECHO        git clone -b stable https://github.com/flutter/flutter.git
+  EXIT /B 1
+)
+
+REM Detect which PowerShell executable is available on the Host
+REM PowerShell version <= 5: PowerShell.exe
+REM PowerShell version >= 6: pwsh.exe
+WHERE /Q pwsh.exe && (
+    SET powershell_executable=pwsh.exe
+) || WHERE /Q PowerShell.exe && (
+    SET powershell_executable=PowerShell.exe
+) || (
+    ECHO Error: PowerShell executable not found.
+    ECHO        Either pwsh.exe or PowerShell.exe must be in your PATH.
+    EXIT /B 1
+)
+
+REM Ensure that bin/cache exists.
+IF NOT EXIST "%cache_dir%" MKDIR "%cache_dir%"
+
+REM If the cache still doesn't exist, fail with an error that we probably don't have permissions.
+IF NOT EXIST "%cache_dir%" (
+  ECHO Error: Unable to create cache directory at
+  ECHO            %cache_dir%
+  ECHO.
+  ECHO        This may be because flutter doesn't have write permissions for
+  ECHO        this path. Try moving the flutter directory to a writable location,
+  ECHO        such as within your home directory.
+  EXIT /B 1
+)
+
+:acquire_lock
+2>NUL (
+  REM "3" is now stderr because of "2>NUL".
+  CALL :subroutine %* 2>&3 9> "%cache_dir%\flutter.bat.lock" || GOTO acquire_lock
+)
+GOTO :after_subroutine
+
+:subroutine
+  PUSHD "%flutter_root%"
+  FOR /f %%r IN ('git rev-parse HEAD') DO SET revision=%%r
+  POPD
+
+  REM The following IF conditions are all linked with a logical OR. However,
+  REM there is no OR operator in batch and a GOTO construct is used as replacement.
+
+  IF NOT EXIST "%engine_stamp%" GOTO do_sdk_update_and_snapshot
+  SET /P dart_required_version=<"%engine_version_path%"
+  SET /P dart_installed_version=<"%engine_stamp%"
+  IF !dart_required_version! NEQ !dart_installed_version! GOTO do_sdk_update_and_snapshot
+  IF NOT EXIST "%snapshot_path%" GOTO do_snapshot
+  IF NOT EXIST "%stamp_path%" GOTO do_snapshot
+  SET /P stamp_value=<"%stamp_path%"
+  IF !stamp_value! NEQ !revision! GOTO do_snapshot
+  SET pubspec_yaml_path=%flutter_tools_dir%\pubspec.yaml
+  SET pubspec_lock_path=%flutter_tools_dir%\pubspec.lock
+  FOR /F %%i IN ('DIR /B /O:D "%pubspec_yaml_path%" "%pubspec_lock_path%"') DO SET newer_file=%%i
+  FOR %%i IN (%pubspec_yaml_path%) DO SET pubspec_yaml_timestamp=%%~ti
+  FOR %%i IN (%pubspec_lock_path%) DO SET pubspec_lock_timestamp=%%~ti
+  IF "%pubspec_yaml_timestamp%" == "%pubspec_lock_timestamp%" SET newer_file=""
+  IF "%newer_file%" EQU "pubspec.yaml" GOTO do_snapshot
+
+  REM Everything is up-to-date - exit subroutine
+  EXIT /B
+
+  :do_sdk_update_and_snapshot
+    ECHO Checking Dart SDK version...
+    SET update_dart_bin=%FLUTTER_ROOT%/bin/internal/update_dart_sdk.ps1
+    REM Escape apostrophes from the executable path
+    SET "update_dart_bin=!update_dart_bin:'=''!"
+    %powershell_executable% -ExecutionPolicy Bypass -Command "Unblock-File -Path '%update_dart_bin%'; & '%update_dart_bin%'"
+    IF "%ERRORLEVEL%" NEQ "0" (
+      ECHO Error: Unable to update Dart SDK. Retrying...
+      timeout /t 5 /nobreak
+      GOTO :do_sdk_update_and_snapshot
+    )
+
+  :do_snapshot
+    IF EXIST "%FLUTTER_ROOT%\version" DEL "%FLUTTER_ROOT%\version"
+    ECHO: > "%cache_dir%\.dartignore"
+    ECHO Building flutter tool...
+    PUSHD "%flutter_tools_dir%"
+
+    REM Makes changes to PUB_ENVIRONMENT only visible to commands within SETLOCAL/ENDLOCAL
+    SETLOCAL
+      SET VERBOSITY=--verbosity=error
+      IF "%CI%" == "true" GOTO on_bot
+      IF "%BOT%" == "true" GOTO on_bot
+      IF "%CONTINUOUS_INTEGRATION%" == "true" GOTO on_bot
+      IF "%CHROME_HEADLESS%" == "1" GOTO on_bot
+      GOTO not_on_bot
+      :on_bot
+        SET PUB_ENVIRONMENT=%PUB_ENVIRONMENT%:flutter_bot
+        SET VERBOSITY=--verbosity=normal
+      :not_on_bot
+      SET PUB_ENVIRONMENT=%PUB_ENVIRONMENT%:flutter_install
+      IF "%PUB_CACHE%" == "" (
+        IF EXIST "%pub_cache_path%" SET PUB_CACHE=%pub_cache_path%
+      )
+
+      SET /A total_tries=10
+      SET /A remaining_tries=%total_tries%-1
+      :retry_pub_upgrade
+        ECHO Running pub upgrade...
+        CALL "%pub%" upgrade "%VERBOSITY%" --no-precompile
+        IF "%ERRORLEVEL%" EQU "0" goto :upgrade_succeeded
+        ECHO Error (%ERRORLEVEL%): Unable to 'pub upgrade' flutter tool. Retrying in five seconds... (%remaining_tries% tries left)
+        timeout /t 5 /nobreak 2>NUL
+        SET /A remaining_tries-=1
+        IF "%remaining_tries%" EQU "0" GOTO upgrade_retries_exhausted
+        GOTO :retry_pub_upgrade
+      :upgrade_retries_exhausted
+        SET exit_code=%ERRORLEVEL%
+        ECHO Error: 'pub upgrade' still failing after %total_tries% tries, giving up.
+        GOTO final_exit
+      :upgrade_succeeded
+    ENDLOCAL
+
+    POPD
+
+    IF "%FLUTTER_TOOL_ARGS%" == "" (
+      "%dart%" --snapshot="%snapshot_path%" --packages="%flutter_tools_dir%\.packages" --no-enable-mirrors "%script_path%"
+    ) else (
+      "%dart%" "%FLUTTER_TOOL_ARGS%" --snapshot="%snapshot_path%" --packages="%flutter_tools_dir%\.packages" "%script_path%"
+    )
+    IF "%ERRORLEVEL%" NEQ "0" (
+      ECHO Error: Unable to create dart snapshot for flutter tool.
+      SET exit_code=%ERRORLEVEL%
+      GOTO :final_exit
+    )
+    >"%stamp_path%" ECHO %revision%
+
+  REM Exit Subroutine
+  EXIT /B
+
+:after_subroutine
diff --git a/bin/shared.sh b/bin/shared.sh
new file mode 100755
index 0000000000..22a5b98209
--- /dev/null
+++ b/bin/shared.sh
@@ -0,0 +1,189 @@
+#!/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 ---------------------------------- #
+#
+# Please keep the logic in this file consistent with the logic in the
+# `shared.bat` script in the same directory to ensure that Flutter & Dart continue
+# to work across all platforms!
+#
+# -------------------------------------------------------------------------- #
+
+set -e
+
+unset CDPATH
+
+function _rmlock () {
+  [ -n "$FLUTTER_UPGRADE_LOCK" ] && rm -f "$FLUTTER_UPGRADE_LOCK"
+}
+
+function retry_upgrade {
+  local total_tries="10"
+  local remaining_tries=$((total_tries - 1))
+  while [[ "$remaining_tries" -gt 0 ]]; do
+    (cd "$FLUTTER_TOOLS_DIR" && "$PUB" upgrade "$VERBOSITY" --no-precompile) && break
+    echo "Error: Unable to 'pub upgrade' flutter tool. Retrying in five seconds... ($remaining_tries tries left)"
+    remaining_tries=$((remaining_tries - 1))
+    sleep 5
+  done
+
+  if [[ "$remaining_tries" == 0 ]]; then
+    echo "Command 'pub upgrade' still failed after $total_tries tries, giving up."
+    return 1
+  fi
+  return 0
+}
+
+function upgrade_flutter () {
+  mkdir -p "$FLUTTER_ROOT/bin/cache"
+
+  # This function is executed with a redirect that pipes the source of
+  # this script into file descriptor 3.
+  #
+  # To ensure that we don't simultaneously update Dart in multiple
+  # parallel instances, we try to obtain an exclusive lock on this
+  # file descriptor (and thus this script's source file) while we are
+  # updating Dart and compiling the script. To do this, we try to use
+  # the command line program "flock", which is available on many
+  # Unix-like platforms, in particular on most Linux distributions.
+  # You give it a file descriptor, and it locks the corresponding
+  # file, having inherited the file descriptor from the shell.
+  #
+  # Complicating matters, there are two major scenarios where this
+  # will not work.
+  #
+  # The first is if the platform doesn't have "flock", for example on Mac.
+  # There is not a direct equivalent, so on platforms that don't have flock,
+  # we fall back to using a lockfile and spinlock with "shlock".  This
+  # doesn't work as well over NFS as it relies on PIDs. Any platform
+  # without either of these tools has no locking at all. To determine if we
+  # have "flock" or "shlock" available, we abuse the "hash" shell built-in.
+  #
+  # The second complication is NFS. On NFS, to obtain an exclusive
+  # lock you need a file descriptor that is open for writing, because
+  # NFS implements exclusive locks by writing, or some such. Thus, we
+  # ignore errors from flock. We do so by using the '|| true' trick,
+  # since we are running in a 'set -e' environment wherein all errors
+  # are fatal, and by redirecting all output to /dev/null, since
+  # users will typically not care about errors from flock and are
+  # more likely to be confused by them than helped.
+  #
+  # For "flock", the lock is released when the file descriptor goes out of
+  # scope,  i.e. when this function returns.  The lock is released via
+  # a trap when using "shlock".
+  if hash flock 2>/dev/null; then
+    flock 3 2>/dev/null || true
+  elif hash shlock 2>/dev/null; then
+    FLUTTER_UPGRADE_LOCK="$FLUTTER_ROOT/bin/cache/.upgrade_lock"
+    while ! shlock -f "$FLUTTER_UPGRADE_LOCK" -p $$ ; do sleep .1 ; done
+    trap _rmlock EXIT
+  fi
+
+  local revision="$(cd "$FLUTTER_ROOT"; git rev-parse HEAD)"
+
+  # Invalidate cache if:
+  #  * SNAPSHOT_PATH is not a file, or
+  #  * STAMP_PATH is not a file with nonzero size, or
+  #  * Contents of STAMP_PATH is not our local git HEAD revision, or
+  #  * pubspec.yaml last modified after pubspec.lock
+  if [[ ! -f "$SNAPSHOT_PATH" || ! -s "$STAMP_PATH" || "$(cat "$STAMP_PATH")" != "$revision" || "$FLUTTER_TOOLS_DIR/pubspec.yaml" -nt "$FLUTTER_TOOLS_DIR/pubspec.lock" ]]; then
+    rm -f "$FLUTTER_ROOT/version"
+    touch "$FLUTTER_ROOT/bin/cache/.dartignore"
+    "$FLUTTER_ROOT/bin/internal/update_dart_sdk.sh"
+    VERBOSITY="--verbosity=error"
+
+    echo Building flutter tool...
+    if [[ "$CI" == "true" || "$BOT" == "true" || "$CONTINUOUS_INTEGRATION" == "true" || "$CHROME_HEADLESS" == "1" ]]; then
+      PUB_ENVIRONMENT="$PUB_ENVIRONMENT:flutter_bot"
+      VERBOSITY="--verbosity=normal"
+    fi
+    export PUB_ENVIRONMENT="$PUB_ENVIRONMENT:flutter_install"
+
+    if [[ -d "$FLUTTER_ROOT/.pub-cache" ]]; then
+      export PUB_CACHE="${PUB_CACHE:-"$FLUTTER_ROOT/.pub-cache"}"
+    fi
+
+    retry_upgrade
+
+    "$DART" --disable-dart-dev $FLUTTER_TOOL_ARGS --snapshot="$SNAPSHOT_PATH" --packages="$FLUTTER_TOOLS_DIR/.packages" --no-enable-mirrors "$SCRIPT_PATH"
+    echo "$revision" > "$STAMP_PATH"
+  fi
+  # The exit here is duplicitous since the function is run in a subshell,
+  # but this serves as documentation that running the function in a
+  # subshell is required to make sure any lockfile created by shlock
+  # is cleaned up.
+  exit $?
+}
+
+# This function is intended to be executed by entrypoints (e.g. `//bin/flutter`
+# and `//bin/dart`)
+function shared::execute() {
+  export FLUTTER_ROOT="$(cd "${BIN_DIR}/.." ; pwd -P)"
+
+  FLUTTER_TOOLS_DIR="$FLUTTER_ROOT/packages/flutter_tools"
+  SNAPSHOT_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.snapshot"
+  STAMP_PATH="$FLUTTER_ROOT/bin/cache/flutter_tools.stamp"
+  SCRIPT_PATH="$FLUTTER_TOOLS_DIR/bin/flutter_tools.dart"
+  DART_SDK_PATH="$FLUTTER_ROOT/bin/cache/dart-sdk"
+
+  DART="$DART_SDK_PATH/bin/dart"
+  PUB="$DART_SDK_PATH/bin/pub"
+
+  # If running over git-bash, overrides the default UNIX
+  # executables with win32 executables
+  case "$(uname -s)" in
+    MINGW32*)
+      DART="$DART.exe"
+      PUB="$PUB.bat"
+      ;;
+  esac
+
+  # Test if running as superuser – but don't warn if running within Docker
+  if [[ "$EUID" == "0" && ! -f /.dockerenv ]]; then
+    echo "   Woah! You appear to be trying to run flutter as root."
+    echo "   We strongly recommend running the flutter tool without superuser privileges."
+    echo "  /"
+    echo "📎"
+  fi
+
+  # Test if Git is available on the Host
+  if ! hash git 2>/dev/null; then
+    echo "Error: Unable to find git in your PATH."
+    exit 1
+  fi
+  # Test if the flutter directory is a git clone (otherwise git rev-parse HEAD
+  # would fail)
+  if [[ ! -e "$FLUTTER_ROOT/.git" ]]; then
+    echo "Error: The Flutter directory is not a clone of the GitHub project."
+    echo "       The flutter tool requires Git in order to operate properly;"
+    echo "       to set up Flutter, run the following command:"
+    echo "       git clone -b stable https://github.com/flutter/flutter.git"
+    exit 1
+  fi
+
+  # To debug the tool, you can uncomment the following lines to enable checked
+  # mode and set an observatory port:
+  # FLUTTER_TOOL_ARGS="--enable-asserts $FLUTTER_TOOL_ARGS"
+  # FLUTTER_TOOL_ARGS="$FLUTTER_TOOL_ARGS --observe=65432"
+
+  (upgrade_flutter) 3< "$PROG_NAME"
+
+  BIN_NAME="$(basename "$PROG_NAME")"
+  case "$BIN_NAME" in
+    flutter*)
+      # FLUTTER_TOOL_ARGS aren't quoted below, because it is meant to
+      # be considered as separate space-separated args.
+      "$DART" --disable-dart-dev --packages="$FLUTTER_TOOLS_DIR/.packages" $FLUTTER_TOOL_ARGS "$SNAPSHOT_PATH" "$@"
+      ;;
+    dart*)
+      "$DART" "$@"
+      ;;
+    *)
+      echo "Error! Executable name $BIN_NAME not recognized!"
+      exit 1
+      ;;
+  esac
+}