GITC: Add repo start support.

Add repo start support for GITC checkouts. If the user is in
the GITC FS view, they can now run repo start to check out
the sources and create a new working branch.

When "repo start" is called on a GITC project, the revision
tag is set to an empty string and saved in a new tag:
old-revision. This tells the GITC filesystem to display the
local copy of the sources when being viewed. The local copy
is created by pulling the project sources and the new branch
is created based off the original project revision.

Updated main.py to setup each command's gitc_manifest when
appropriate.

Updated repo sync's logic to sync opened projects and
updating the GITC manifest file for the rest.

Change-Id: I7e4809d1c4fc43c69b26f2f1bebe45aab0cae628

subcmds/start.py

@@ -14,11 +14,15 @@
 # limitations under the License.
 
 from __future__ import print_function
+import os
 import sys
+
 from command import Command
 from git_config import IsId
 from git_command import git
+import gitc_utils
 from progress import Progress
+from project import SyncBuffer
 
 class Start(Command):
   common = True
@@ -53,20 +57,50 @@ revision specified in the manifest.
         print("error: at least one project must be specified", file=sys.stderr)
         sys.exit(1)
 
-    all_projects = self.GetProjects(projects)
+    proj_name_to_gitc_proj_dict = {}
+    if self.gitc_manifest:
+      all_projects = self.GetProjects(projects, manifest=self.gitc_manifest,
+                                      missing_ok=True)
+      for project in all_projects:
+        if project.old_revision:
+          project.already_synced = True
+        else:
+          project.already_synced = False
+          project.old_revision = project.revisionExpr
+        proj_name_to_gitc_proj_dict[project.name] = project
+        project.revisionExpr = None
+      # Save the GITC manifest.
+      gitc_utils.save_manifest(self.gitc_manifest)
 
+    all_projects = self.GetProjects(projects,
+                                    missing_ok=bool(self.gitc_manifest))
     pm = Progress('Starting %s' % nb, len(all_projects))
     for project in all_projects:
       pm.update()
+      if self.gitc_manifest:
+        gitc_project = proj_name_to_gitc_proj_dict[project.name]
+        # Sync projects that have already been opened.
+        if not gitc_project.already_synced:
+          proj_localdir = os.path.join(self.gitc_manifest.gitc_client_dir,
+                                       project.relpath)
+          project.worktree = proj_localdir
+          if not os.path.exists(proj_localdir):
+            os.makedirs(proj_localdir)
+          project.Sync_NetworkHalf()
+          sync_buf = SyncBuffer(self.manifest.manifestProject.config)
+          project.Sync_LocalHalf(sync_buf)
+          project.revisionExpr = gitc_project.old_revision
+
       # If the current revision is a specific SHA1 then we can't push back
       # to it; so substitute with dest_branch if defined, or with manifest
       # default revision instead.
+      branch_merge = ''
       if IsId(project.revisionExpr):
         if project.dest_branch:
-          project.revisionExpr = project.dest_branch
+          branch_merge = project.dest_branch
         else:
-          project.revisionExpr = self.manifest.default.revisionExpr
-      if not project.StartBranch(nb):
+          branch_merge = self.manifest.default.revisionExpr
+      if not project.StartBranch(nb, branch_merge=branch_merge):
         err.append(project)
     pm.end()