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>

project.py

@@ -782,7 +782,8 @@ class Project(object):
       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 @@ class Project(object):
     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

subcmds/start.py

@@ -16,6 +16,7 @@
 import sys
 from command import Command
 from git_command import git
+from progress import Progress
 
 class Start(Command):
   common = True
@@ -38,9 +39,14 @@ revision specified in the manifest.
       sys.exit(1)
 
     err = []
-    for project in self.GetProjects(args[1:]):
+    all = self.GetProjects(args[1:])
+
+    pm = Progress('Starting %s' % nb, len(all))
+    for project in all:
+      pm.update()
       if not project.StartBranch(nb):
         err.append(project)
+    pm.end()
 
     if err:
       err.sort()