Summary:
AR/VR Engineering does AOSP development using Git and Google Repo. This is rough at times because FB Dev Infra doesn't support these tools in a lot of critical use cases. This commit contains a very rough prototype of a hg convert extension to support Google Repo as a source.
What this commit does:
1. Finds all of the heads in all of the git projects in the Grepo and imports their commit histories into mercurial.
2. Merges those commits into a single commit history that represents the default manifest in the current branch.
What this commit doesn't do:
1. Explore the space of all manifests that have ever existed in the manifest project and update directory branches based on those.
Reviewed By: tchebb
Differential Revision: D14944252
fbshipit-source-id: b292025ccac06d02b347e35839215eedfd151a5d
