Add option on sync to avoid fetching from remotes for existing sha1

In 2fb6466f795eb30c1dfa598501f5b5d2981e6a5f an optimisation was
added to avoid fetching from remotes if the project is fixed to
a revision and the revision is already available locally.

This causes problems for users who expect all objects to be
fetched by default.

Change the logic so that the optimized behaviour is only enabled if
an option is explicitly given to repo sync.

Change-Id: I3b2794ddd8e0071b1787e166463cd8347ca9e24f

project.py

@@ -529,7 +529,8 @@ class Project(object):
                upstream=None,
                parent=None,
                is_derived=False,
-               dest_branch=None):
+               dest_branch=None,
+               optimized_fetch=False):
     """Init a Project object.
 
     Args:
@@ -551,6 +552,8 @@ class Project(object):
       is_derived: False if the project was explicitly defined in the manifest;
                   True if the project is a discovered submodule.
       dest_branch: The branch to which to push changes for review by default.
+      optimized_fetch: If True, when a project is set to a sha1 revision, only
+                       fetch from the remote if the sha1 is not present locally.
     """
     self.manifest = manifest
     self.name = name
@@ -579,6 +582,7 @@ class Project(object):
     self.upstream = upstream
     self.parent = parent
     self.is_derived = is_derived
+    self.optimized_fetch = optimized_fetch
     self.subprojects = []
 
     self.snapshots = {}
@@ -1060,7 +1064,8 @@ class Project(object):
       current_branch_only=False,
       clone_bundle=True,
       no_tags=False,
-      archive=False):
+      archive=False,
+      optimized_fetch=False):
     """Perform only the network IO portion of the sync process.
        Local working directory/branch state is not affected.
     """
@@ -1129,8 +1134,9 @@ class Project(object):
       elif self.manifest.default.sync_c:
         current_branch_only = True
 
-    has_sha1 = ID_RE.match(self.revisionExpr) and self._CheckForSha1()
-    if (not has_sha1  #Need to fetch since we don't already have this revision
+    need_to_fetch = not (optimized_fetch and \
+      (ID_RE.match(self.revisionExpr) and self._CheckForSha1()))
+    if (need_to_fetch
         and not self._RemoteFetch(initial=is_new, quiet=quiet, alt_dir=alt_dir,
                                   current_branch_only=current_branch_only,
                                   no_tags=no_tags)):

subcmds/sync.py

@@ -131,6 +131,10 @@ of a project from server.
 The -c/--current-branch option can be used to only fetch objects that
 are on the branch specified by a project's revision.
 
+The --optimized-fetch option can be used to only fetch projects that
+are fixed to a sha1 revision if the sha1 revision does not already
+exist locally.
+
 SSH Connections
 ---------------
 
@@ -206,6 +210,9 @@ later is required to fix a server side protocol bug.
     p.add_option('--no-tags',
                  dest='no_tags', action='store_true',
                  help="don't fetch tags")
+    p.add_option('--optimized-fetch',
+                 dest='optimized_fetch', action='store_true',
+                 help='only fetch projects fixed to sha1 if revision does not exist locally')
     if show_smart:
       p.add_option('-s', '--smart-sync',
                    dest='smart_sync', action='store_true',
@@ -275,7 +282,8 @@ later is required to fix a server side protocol bug.
           quiet=opt.quiet,
           current_branch_only=opt.current_branch_only,
           clone_bundle=not opt.no_clone_bundle,
-          no_tags=opt.no_tags, archive=self.manifest.IsArchive)
+          no_tags=opt.no_tags, archive=self.manifest.IsArchive,
+          optimized_fetch=opt.optimized_fetch)
         self._fetch_times.Set(project, time.time() - start)
 
         # Lock around all the rest of the code, since printing, updating a set
@@ -615,7 +623,8 @@ later is required to fix a server side protocol bug.
     if not opt.local_only:
       mp.Sync_NetworkHalf(quiet=opt.quiet,
                           current_branch_only=opt.current_branch_only,
-                          no_tags=opt.no_tags)
+                          no_tags=opt.no_tags,
+                          optimized_fetch=opt.optimized_fetch)
 
     if mp.HasChanges:
       syncbuf = SyncBuffer(mp.config)