Cache dependency tree

[russellpierce]

Just walking the dependency tree for a lockfile can take a while. This makes starting up with lockbox a tad slow. It seems like one could digest the lockfile and store a cache of the dependency tree for subsequent start-ups to allow things to go a bit faster.

[robertzk]

Agreed, this should be specifiable by an option. In our use case, we update dependencies of dependencies frequently and typically the full walk is preferred on every startup, but I understand this is atypical for most environments.

[russellpierce]

For a given .yml the dependency tree may change:

1. If autoinstall: true
2. When package A depends on B and A is in the yml but B is not and B is updated between runs?

... Are there some other cases that immediately occur to you?