init: add -o, --origin to name manifest remote

The -o option permits the user to control the name of the manifest's
remote, which normally is hardcoded to be 'origin', but can differ
because we derive it at runtime from the configuration file.

Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/subcmds/init.py b/subcmds/init.py
index 0586721..53c3a01 100644
--- a/subcmds/init.py
+++ b/subcmds/init.py
@@ -62,6 +62,10 @@
     g.add_option('-b', '--manifest-branch',
                  dest='manifest_branch',
                  help='manifest branch or revision', metavar='REVISION')
+    g.add_option('-o', '--origin',
+                 dest='manifest_origin',
+                 help="use REMOTE instead of 'origin' to track upstream",
+                 metavar='REMOTE')
     if isinstance(self.manifest, XmlManifest) \
     or not self.manifest.manifestProject.Exists:
       g.add_option('-m', '--manifest-name',
@@ -84,30 +88,42 @@
                  dest='no_repo_verify', action='store_true',
                  help='do not verify repo source code')
 
-  def _SyncManifest(self, opt):
+  def _ApplyOptions(self, opt, is_new):
     m = self.manifest.manifestProject
-    is_new = not m.Exists
 
     if is_new:
-      if not opt.manifest_url:
-        print >>sys.stderr, 'fatal: manifest url (-u) is required.'
-        sys.exit(1)
-
-      if not opt.quiet:
-        print >>sys.stderr, 'Getting manifest ...'
-        print >>sys.stderr, '   from %s' % opt.manifest_url
-      m._InitGitDir()
+      if opt.manifest_origin:
+        m.remote.name = opt.manifest_origin
 
       if opt.manifest_branch:
         m.revisionExpr = opt.manifest_branch
       else:
         m.revisionExpr = 'refs/heads/master'
     else:
+      if opt.manifest_origin:
+        print >>sys.stderr, 'fatal: cannot change origin name'
+        sys.exit(1)
+
       if opt.manifest_branch:
         m.revisionExpr = opt.manifest_branch
       else:
         m.PreSync()
 
+  def _SyncManifest(self, opt):
+    m = self.manifest.manifestProject
+    is_new = not m.Exists
+
+    if is_new:
+      if not opt.manifest_url:
+        print >>sys.stderr, 'fatal: manifest url (-u) is required.'
+        sys.exit(1)
+
+      if not opt.quiet:
+        print >>sys.stderr, 'Getting manifest ...'
+        print >>sys.stderr, '   from %s' % opt.manifest_url
+      m._InitGitDir()
+
+    self._ApplyOptions(opt, is_new)
     if opt.manifest_url:
       r = m.GetRemote(m.remote.name)
       r.url = opt.manifest_url