Shift git version fetching to tools/gn (#51175)

Avoids GN invoking python scripts that run git commands to determine git
hashes.

Part of flutter/flutter#144430

Author: zanderso

shell/version/version.gni

@@ -14,35 +14,6 @@ declare_args() {
 
 _flutter_root = "//flutter"
 
-if (engine_version == "") {
-  engine_version_lines =
-      exec_script("//flutter/build/git_revision.py",
-                  [
-                    "--repository",
-                    rebase_path(_flutter_root, "", _flutter_root),
-                  ],
-                  "list lines")
-  engine_version = engine_version_lines[0]
-}
-
-if (skia_version == "") {
-  skia_version_lines = exec_script(
-          "//flutter/build/git_revision.py",
-          [
-            "--repository",
-            rebase_path("//flutter/third_party/skia", "", _flutter_root),
-          ],
-          "list lines")
-  skia_version = skia_version_lines[0]
-}
-
-if (dart_version == "") {
-  dart_version_lines =
-      exec_script("//flutter/build/git_revision.py",
-                  [
-                    "--repository",
-                    rebase_path("$dart_src", "", _flutter_root),
-                  ],
-                  "list lines")
-  dart_version = dart_version_lines[0]
-}
+assert(engine_version != "", "The engine_version argument must be supplied")
+assert(skia_version != "", "The skia_version argument must be supplied")
+assert(dart_version != "", "The dart_version argument must be supplied")

tools/gn

@@ -344,6 +344,40 @@ def setup_apple_sdks():
   return sdks_gn_args
 
 
+def get_repository_version(repository):
+  'Returns the Git HEAD for the supplied repository path as a string.'
+  if not os.path.exists(repository):
+    raise IOError('path does not exist')
+
+  git = 'git'
+  if sys.platform.startswith(('cygwin', 'win')):
+    git = 'git.bat'
+  version = subprocess.check_output([
+      git,
+      '-C',
+      repository,
+      'rev-parse',
+      'HEAD',
+  ])
+
+  return str(version.strip(), 'utf-8')
+
+
+def setup_git_versions():
+  revision_args = {}
+
+  engine_path = os.path.join(SRC_ROOT, 'flutter')
+  revision_args['engine_version'] = get_repository_version(engine_path)
+
+  skia_path = os.path.join(SRC_ROOT, 'flutter', 'third_party', 'skia')
+  revision_args['skia_version'] = get_repository_version(skia_path)
+
+  dart_path = os.path.join(SRC_ROOT, 'third_party', 'dart')
+  revision_args['dart_version'] = get_repository_version(dart_path)
+
+  return revision_args
+
+
 def to_gn_args(args):
   if args.simulator:
     if args.target_os != 'ios':
@@ -355,6 +389,8 @@ def to_gn_args(args):
 
   gn_args['is_debug'] = args.unoptimized
 
+  gn_args.update(setup_git_versions())
+
   gn_args.update(setup_goma(args))
 
   gn_args.update(setup_rbe(args))
@@ -697,6 +733,8 @@ def to_gn_args(args):
   # for a host Windows build and make GN think we will be building ANGLE.
   # Angle is not used on Mac hosts as there are no tests for the OpenGL backend.
   if is_host_build(args) or (args.target_os == 'android' and get_host_os() == 'win'):
+    # Don't include git commit information.
+    gn_args['angle_enable_commit_id'] = False
     # Do not build unnecessary parts of the ANGLE tree.
     gn_args['angle_build_all'] = False
     gn_args['angle_has_astc_encoder'] = False