- Unmerge appropriate packages during upgrades and downgrades.
- Calculate time spent in dependency generation to the tenth of a second.
- Only track dependencies of packages that are actually being installed.
- Ignore PDEPEND, as it has no impact on dependency ordering.
- Only break dependency chains that go against Portage's install order.
- Rename Failed -> Retrying.
- Print emerge command lines as they are run.
TEST=Emerged hard-host-depends and ran build_packages with parallel_emerge
BUG=none
Review URL: http://codereview.chromium.org/2886010
Include checked in parallel emerge,
with an optional (default false) argument
in build_image to turn it on.
Review URL: http://codereview.chromium.org/2827037
