git: use new python script to bootstrap git on windows

BUG=635421, 629679

Recipe-Tryjob-Bypass-Reason: downstream changes expected
Review-Url: https://codereview.chromium.org/2264583002

recipe_modules/git/api.py

@@ -41,9 +41,10 @@ class GitApi(recipe_api.RecipeApi):
     """Ensures that depot_tools/git.bat actually exists."""
     if not self.m.platform.is_win or self.initialized_win_git:
       return
-    self.m.step(
+    self.m.python(
         'ensure git tooling on windows',
-        [self.package_repo_resource('bootstrap', 'win', 'win_tools.bat')],
+        self.package_repo_resource('bootstrap', 'win', 'git_bootstrap.py'),
+        ['--verbose'],
         infra_step=True,
         cwd=self.package_repo_resource(),
         timeout=300)

recipe_modules/git/example.expected/platform_win.json

 [
   {
     "cmd": [
-      "RECIPE_PACKAGE_REPO[depot_tools]\\bootstrap\\win\\win_tools.bat"
+      "python",
+      "-u",
+      "RECIPE_PACKAGE_REPO[depot_tools]\\bootstrap\\win\\git_bootstrap.py",
+      "--verbose"
     ],
     "cwd": "RECIPE_PACKAGE_REPO[depot_tools]",
     "name": "ensure git tooling on windows",

recipe_modules/tryserver/example.expected/with_wrong_patch.json

 [
   {
     "cmd": [
-      "RECIPE_PACKAGE_REPO[depot_tools]\\bootstrap\\win\\win_tools.bat"
+      "python",
+      "-u",
+      "RECIPE_PACKAGE_REPO[depot_tools]\\bootstrap\\win\\git_bootstrap.py",
+      "--verbose"
     ],
     "cwd": "RECIPE_PACKAGE_REPO[depot_tools]",
     "name": "ensure git tooling on windows",

recipe_modules/tryserver/example.expected/with_wrong_patch_new.json

 [
   {
     "cmd": [
-      "RECIPE_PACKAGE_REPO[depot_tools]\\bootstrap\\win\\win_tools.bat"
+      "python",
+      "-u",
+      "RECIPE_PACKAGE_REPO[depot_tools]\\bootstrap\\win\\git_bootstrap.py",
+      "--verbose"
     ],
     "cwd": "RECIPE_PACKAGE_REPO[depot_tools]",
     "name": "ensure git tooling on windows",