Actually disable collision-protect in parallel_emerge.

parallel_emerge

 #!/usr/bin/python2.6
 # Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Program to run emerge in parallel, for significant speedup.
 
 Usage:
  ./parallel_emerge [--board=BOARD] [--workon=PKGS] [--no-workon-deps]
                    [emerge args] package"
@@ skipping 297 matching lines @@
     # reuse here.
     if "--debug" in opts:
       os.environ["PORTAGE_DEBUG"] = "1"
     if "--config-root" in opts:
       os.environ["PORTAGE_CONFIGROOT"] = opts["--config-root"]
     if "--root" in opts:
       os.environ["ROOT"] = opts["--root"]
     if "--accept-properties" in opts:
       os.environ["ACCEPT_PROPERTIES"] = opts["--accept-properties"]
 
+    # Portage has two flags for doing collision protection: collision-protect
+    # and protect-owned. The protect-owned feature is enabled by default and
+    # is quite useful: it checks to make sure that we don't have multiple
+    # packages that own the same file. The collision-protect feature is more
+    # strict, and less useful: it fails if it finds a conflicting file, even
+    # if that file was created by an earlier ebuild that failed to install.
+    #
+    # We want to disable collision-protect here because we don't handle
+    # failures during the merge step very well. Sometimes we leave old files
+    # lying around and they cause problems, so for now we disable the flag.
+    # TODO(davidjames): Look for a better solution.
+    features = os.environ.get("FEATURES", "") + " -collision-protect"
+    os.environ["FEATURES"] = features
+
     # Now that we've setup the necessary environment variables, we can load the
     # emerge config from disk.
     settings, trees, mtimedb = load_emerge_config()
 
     # Check whether our portage tree is out of date. Typically, this happens
     # when you're setting up a new portage tree, such as in setup_board and
     # make_chroot. In that case, portage applies a bunch of global updates
     # here. Once the updates are finished, we need to commit any changes
     # that the global update made to our mtimedb, and reload the config.
     #
@@ skipping 21 matching lines @@
       opts.setdefault("--resume", True)
     if "--buildpkgonly" in opts:
       # --buildpkgonly will not merge anything, so it overrides all binary
       # package options.
       for opt in ("--getbinpkg", "--getbinpkgonly",
                   "--usepkg", "--usepkgonly"):
         opts.pop(opt, None)
     if (settings.get("PORTAGE_DEBUG", "") == "1" and
         "python-trace" in settings.features):
       portage.debug.set_trace(True)
-    # Since we don't have locking around merges, the collision-protect
-    # feature doesn't make sense.
-    settings.features.discard("collision-protect")
 
     # Complain about unsupported options
     for opt in ("--ask", "--ask-enter-invalid", "--complete-graph",
                 "--resume", "--skipfirst"):
       if opt in opts:
         print "%s is not supported by parallel_emerge" % opt
         sys.exit(1)
 
     # Make emerge specific adjustments to the config (e.g. colors!)
     adjust_configs(opts, trees)
@@ skipping 899 matching lines @@
       for db_pkg in final_db.match_pkgs(pkg):
         print "Adding %s to world" % db_pkg.cp
         new_world_pkgs.append(db_pkg.cp)
     if new_world_pkgs:
       world_set.update(new_world_pkgs)
 
   print "Done"
 
 if __name__ == "__main__":
   main()