Use git exec candidate list on all platforms for build (flutter#34294)

* Use git exec candidate list on all platforms for build

build/git_revision.py now uses a git executable name search list on all
platforms, avoiding issues with some Windows installations.

* Moving python import to top to satisfy linter

* Fixing format error and removing unneeded check

* Adding git candidate search to githooks setup.py

* Adding missing COM initialization to
flutter_tester executable on Windows

* Revert "Adding missing COM initialization to"

Reason: Added to incorrect branch

This reverts commit 1b0da56.

* Format fix for setup.py

build/git_revision.py

@@ -10,21 +10,20 @@
 import subprocess
 import os
 import argparse
-
-
-def is_windows():
-  os_id = sys.platform
-  return os_id.startswith('win32') or os_id.startswith('cygwin')
+from shutil import which  # Natively supported since python 3.3
 
 
 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 is_windows():
-    git = 'git.bat'
+  git_candidates = ['git', 'git.sh', 'git.bat']
+  git = next(filter(which, git_candidates), None)
+  if git is None:
+    candidates = "', '".join(git_candidates)
+    raise IOError(f"Looks like GIT is not on the path. Tried '{candidates}'")
+
   version = subprocess.check_output([
       git,
       '-C',

tools/githooks/setup.py

@@ -10,6 +10,7 @@
 import os
 import subprocess
 import sys
+from shutil import which  # Natively supported since python 3.3
 
 SRC_ROOT = os.path.dirname(
     os.path.dirname(
@@ -19,17 +20,13 @@
 FLUTTER_DIR = os.path.join(SRC_ROOT, 'flutter')
 
 
-def IsWindows():
-  os_id = sys.platform
-  return os_id.startswith('win32') or os_id.startswith('cygwin')
-
-
 def Main(argv):
-  git = 'git'
   githooks = os.path.join(FLUTTER_DIR, 'tools', 'githooks')
-  if IsWindows():
-    git = 'git.bat'
-    githooks = os.path.join(githooks, 'windows')
+  git_candidates = ['git', 'git.sh', 'git.bat']
+  git = next(filter(which, git_candidates), None)
+  if git is None:
+    candidates = "', '".join(git_candidates)
+    raise IOError(f"Looks like GIT is not on the path. Tried '{candidates}'")
   result = subprocess.run([
       git,
       'config',