tree 4c7ec381f2452d3ae4ed5332230a8d7a61e6ec2b
parent b25ea555c39cd500740acb74fa9f1dab71588266
author David James <davidjames@google.com> 1381536199 -0700
committer David James <davidjames@google.com> 1381790072 -0700

repo: Support multiple branches for the same project.

It is often useful to be able to include the same project more than
once, but with different branches and placed in different paths in the
workspace. Add this feature.

This CL adds the concept of an object directory. The object directory
stores objects that can be shared amongst several working trees. For
newly synced repositories, we set up the git repo now to share its
objects with an object repo.

Each worktree for a given repo shares objects, but has an independent
set of references and branches. This ensures that repo only has to
update the objects once; however the references for each worktree are
updated separately. Storing the references separately is needed to
ensure that commits to a branch on one worktree will not change the
HEAD commits of the others.

One nice side effect of sharing objects between different worktrees is
that you can easily cherry-pick changes between the two worktrees
without needing to fetch them.

Bug: Issue 141
Change-Id: I5e2f4e1a7abb56f9d3f310fa6fd0c17019330ecd