Simplify the initialization of Git objects in Host.

third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/git.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/git.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/git.py b/third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/git.py
index 442173fb86d31016846e588b3f92eaaf9ec7738b..0e45687f52537374ae961b21983ed25adccf4b2b 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/git.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/common/checkout/scm/git.py
@@ -48,12 +48,45 @@ class Git(object):
 
     executable_name = 'git'
 
-    def __init__(self, cwd, executive=None, filesystem=None):
-        self.cwd = cwd
+    def __init__(self, cwd=None, executive=None, filesystem=None):
         self._executive = executive or Executive()
         self._filesystem = filesystem or FileSystem()
+
+        self.cwd = cwd or self._filesystem.abspath(self._filesystem.getcwd())
+        if not Git.in_working_directory(self.cwd, executive=self._executive):
+            module_directory = self._filesystem.abspath(
+                self._filesystem.dirname(self._filesystem.path_to_module(self.__module__)))
+            _log.info('The current directory (%s) is not in a git repo, trying directory %s.',
+                      cwd, module_directory)
+            if Git.in_working_directory(module_directory, executive=self._executive):
+                self.cwd = module_directory
+            _log.error('Failed to find Git repo for %s or %s', cwd, module_directory)
+
+        self._init_executable_name()
         self.checkout_root = self.find_checkout_root(self.cwd)
 
+    def _init_executable_name(self):
+        # FIXME: This is a hack and should be removed.
+        try:
+            self._executive.run_command(['git', 'help'])
+        except OSError:
+            try:
+                self._executive.run_command(['git.bat', 'help'])
+                # The Win port uses the depot_tools package, which contains a number
+                # of development tools, including Python and git. Instead of using a
+                # real git executable, depot_tools indirects via a batch file, called
+                # "git.bat". This batch file allows depot_tools to auto-update the real
+                # git executable, which is contained in a subdirectory.
+                #
+                # That's all fine and good, except that subprocess.popen can detect
+                # the difference between a real git executable and batch file when we
+                # don't use shell=True. Rather than use shell=True on Windows,
+                # we set the executable name on a class variable.

[jeffcarp, 2017/02/01 17:27:03]

Nit: I think this should be 'instance variable' not class variable

[qyearsley, 2017/02/01 17:46:13]

You're right, it's set here as an instance variable, although it was originally
set on the class object on line 49.

Messing around with this a bit:
...   x = 1
...   def set_x(self, new_x):
...     self.x = new_x
... 
1
1
20
1

But actually, I'm not sure I really understand the second paragraph here -- I've
read we're not supposed to use shell=True since there's some security issue, and
I guess that saying that subprocess.Popen detects the difference between git and
git.bat means that just "git" doesn't work on windows and won't use git.bat, so
we want to explicitly invoke git with "git.bat".

In the latest patchset I removed the second paragraph; does that seem OK?

[jeffcarp, 2017/02/01 18:27:55]

👍

+                _log.debug('Engaging git.bat Windows hack.')
+                self.executable_name = 'git.bat'
+            except OSError:
+                _log.debug('Failed to engage git.bat Windows hack.')
+
     def _run_git(self,
                  command_args,
                  cwd=None,