Perform Git operations without changing CWD.

recipe_engine/package.py

Index: recipe_engine/package.py
diff --git a/recipe_engine/package.py b/recipe_engine/package.py
index 57f279070e0a20621d11a7d1a1da650df2b24542..9d5d6287a794333920a867b2db8914585505dc65 100644
--- a/recipe_engine/package.py
+++ b/recipe_engine/package.py
@@ -196,6 +196,9 @@ class GitRepoSpec(RepoSpec):
             'branch="%(branch)s", revision="%(revision)s", '
             'path="%(path)s"}' % self.__dict__)
 
+  def run_git(self, cwd, *args):
+    _run_cmd([self._git, '--git-dir', os.path.join(cwd, '.git')] + list(args))
+
   def checkout(self, context):
     dep_dir = self._dep_dir(context)
     logging.info('Freshening repository %s' % dep_dir)
@@ -206,11 +209,11 @@ class GitRepoSpec(RepoSpec):
       raise UncleanFilesystemError('%s exists but is not a git repo' % dep_dir)
 
     try:
-      subprocess.check_output([self._git, 'rev-parse', '-q', '--verify',
-                               '%s^{commit}' % self.revision], cwd=dep_dir)
+      self.run_git(dep_dir, 'rev-parse', '-q', '--verify',
+                    '%s^{commit}' % self.revision)
     except subprocess.CalledProcessError:
-      _run_cmd([self._git, 'fetch'], cwd=dep_dir)
-    _run_cmd([self._git, 'reset', '-q', '--hard', self.revision], cwd=dep_dir)
+      self.run_git(dep_dir, 'fetch')
+    self.run_git(dep_dir, 'reset', '-q', '--hard', self.revision)
 
   def check_checkout(self, context):
     dep_dir = self._dep_dir(context)
@@ -259,7 +262,7 @@ class GitRepoSpec(RepoSpec):
 
   def _raw_updates(self, context, subdir):
     self.checkout(context)
-    _run_cmd([self._git, 'fetch'], cwd=self._dep_dir(context))
+    self.run_git(self._dep_dir(context), fetch)

[Paweł Hajdan Jr., 2016/03/31 17:35:37]

Shouldn't fetch be changed to 'fetch'? Just checking.

[dnj, 2016/03/31 17:47:50]

Done.

     args = [self._git, 'rev-list', '--reverse',
             '%s..origin/%s' % (self.revision, self.branch)]
     if subdir: