Add progress meter to 'repo start'

This is mostly useful if the number of projects to switch is many
(e.g. all of Android) and a large number of them are behind the
current manifest revision.  We wind up needing to run git just to
make the working tree match, and that often makes the command take
a couple of seconds longer than we'd like.

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/project.py b/project.py
index 0a761ef..10a9b25 100644
--- a/project.py
+++ b/project.py
@@ -782,7 +782,8 @@
       cmd = ['checkout', name, '--']
       return GitCommand(self,
                         cmd,
-                        capture_stdout = True).Wait() == 0
+                        capture_stdout = True,
+                        capture_stderr = True).Wait() == 0
 
     branch = self.GetBranch(name)
     branch.remote = self.GetRemote(self.remote.name)
@@ -817,7 +818,8 @@
     cmd = ['checkout', '-b', branch.name, rev]
     if GitCommand(self,
                   cmd,
-                  capture_stdout = True).Wait() == 0:
+                  capture_stdout = True,
+                  capture_stderr = True).Wait() == 0:
       branch.Save()
       return True
     return False