Implement git-drover.

git_cache.py

Index: git_cache.py
diff --git a/git_cache.py b/git_cache.py
index 52e42c59274781f580491428b67afa4d6bf66280..9b7082ba9b660b0f8ec7d153d12ae02fea017277 100755
--- a/git_cache.py
+++ b/git_cache.py
@@ -28,6 +28,7 @@ except NameError:
   class WinErr(Exception):
     pass
 
+
 class LockError(Exception):
   pass
 
@@ -151,6 +152,30 @@ class Mirror(object):
     self.mirror_path = os.path.join(self.GetCachePath(), self.basedir)
     self.print = print_func or print
 
+  @classmethod
+  def from_repo(cls, path=None):
+    """Returns Mirror if path is in a cached repo, else None."""
+    args = ['-C', path] if path else []
+    args = [cls.git_exe] + args + ['rev-parse', '--git-dir']
+    git_path = subprocess.check_output(args).strip()
+    alt_path = os.path.join(git_path, 'objects', 'info', 'alternates')
+
+    if os.path.exists(alt_path):
+      with open(alt_path, 'rb') as alt:
+        mirror_path = alt.read().strip()
+      mirror_path = os.path.dirname(mirror_path)
+      cache_path = os.path.dirname(mirror_path)
+      if os.path.exists(mirror_path):
+        url = subprocess.check_output(
+            [cls.git_exe, '-C', mirror_path, 'config', 'remote.origin.url']
+        ).strip()
+
+        # TODO(iannucci): cache_path should NOT be a class attribute. Maybe
+        # a `default_cache_path`, but not the actual path.
+        cls.SetCachePath(cache_path)
+
+        return cls(url)
+
   @staticmethod
   def UrlToCacheDir(url):
     """Convert a git url to a normalized form for the cache dir path."""
@@ -222,7 +247,7 @@ class Mirror(object):
         refspec = '+refs/%s/*:refs/%s/*' % (ref, ref)
       self.RunGit(['config', '--add', 'remote.origin.fetch', refspec], cwd=cwd)
 
-  def bootstrap_repo(self, directory):
+  def bootstrap_repo(self, directory, verbose):
     """Bootstrap the repo from Google Stroage if possible."""
 
     python_fallback = False
@@ -248,8 +273,10 @@ class Mirror(object):
     # Download zip file to a temporary directory.
     try:
       tempdir = tempfile.mkdtemp()
-      self.print('Downloading %s' % latest_checkout)
-      code, out, err = gsutil.check_call('cp', latest_checkout, tempdir)
+      if not verbose:
+        self.print('Downloading %s' % latest_checkout)
+      code, out, err = gsutil.check_call('cp', latest_checkout, tempdir,
+                                         verbose=verbose)
       if code:
         self.print('%s\n%s' % (out, err))
         return False
@@ -287,7 +314,7 @@ class Mirror(object):
     return os.path.isfile(os.path.join(self.mirror_path, 'config'))
 
   def populate(self, depth=None, shallow=False, bootstrap=False,
-               verbose=False):
+               verbose=False, fetch_specs=()):
     if shallow and not depth:
       depth = 10000
     gclient_utils.safe_makedirs(self.GetCachePath())
@@ -308,7 +335,8 @@ class Mirror(object):
         gclient_utils.rmtree(self.mirror_path)
         tempdir = tempfile.mkdtemp(
             suffix=self.basedir, dir=self.GetCachePath())
-        bootstrapped = not depth and bootstrap and self.bootstrap_repo(tempdir)
+        bootstrapped = (not depth and bootstrap and
+                        self.bootstrap_repo(tempdir, verbose))
         if not bootstrapped:
           self.RunGit(['init', '--bare'], cwd=tempdir)
       else:
@@ -320,7 +348,7 @@ class Mirror(object):
       rundir = tempdir or self.mirror_path
       self.config(rundir)
       fetch_cmd = ['fetch'] + v + d + ['origin']
-      fetch_specs = subprocess.check_output(
+      fetch_specs = fetch_specs or subprocess.check_output(
           [self.git_exe, 'config', '--get-all', 'remote.origin.fetch'],
           cwd=rundir).strip().splitlines()
       for spec in fetch_specs: