Allow repo forall to skip repo and manifest mirrors

When running `repo forall` in a mirror client, allow the caller to
request skipping over the tools/repo.git and manifest.git repository
as these aren't typically listed in the manifest, and thus don't
appear in a normal (non-mirror) client checkout.

Bug: REPO-18
Signed-off-by: Shawn O. Pearce <sop@google.com>

manifest.py

@@ -287,6 +287,7 @@ class Manifest(object):
                         worktree = None,
                         relpath = None,
                         revision = m.revision)
+      project.metaProject = True
       self._projects[project.name] = project
 
   def _ParseRemote(self, node):

project.py

@@ -223,6 +223,7 @@ class Project(object):
     self.snapshots = {}
     self.extraRemotes = {}
     self.copyfiles = []
+    self.metaProject = False
     self.config = GitConfig.ForRepository(
                     gitdir = self.gitdir,
                     defaults =  self.manifest.globalConfig)
@@ -1167,6 +1168,7 @@ class MetaProject(Project):
                      remote = Remote('origin'),
                      relpath = '.repo/%s' % name,
                      revision = 'refs/heads/master')
+    self.metaProject = True
 
   def PreSync(self):
     if self.Exists:

subcmds/forall.py

@@ -54,6 +54,11 @@ not redirected.
 """
 
   def _Options(self, p):
+    p.add_option('--manifest-only',
+                 help='Exclude repo and manifest mirrors',
+                 dest='manifest_only',
+                 action='store_true')
+
     def cmd(option, opt_str, value, parser):
       setattr(parser.values, option.dest, list(parser.rargs))
       while parser.rargs:
@@ -81,6 +86,9 @@ not redirected.
     mirror = self.manifest.IsMirror
     rc = 0
     for project in self.GetProjects(args):
+      if mirror and project.metaProject and opt.manifest_only:
+        continue
+
       env = dict(os.environ.iteritems())
       def setenv(name, val):
         if val is None: