Feature Request: Don't fetch source updates if needed revision is found locally

[mattfarina]

Dep takes a long time to install packages when the cache already has the needed commits. Please correct me if I'm wrong but, it appears dep is going out to the network for updates even when it may not need to.

For the case the Gopkg.lock is present, dep ensure is being run, and nothing is being updated (the lock file isn't changing) dep still goes out to the network.

Is there a way the needed commit could be checked for in the cache and if present skip updating?

[jmank88]

We've been working towards a persistent cache in #431, currently at #1250 and on hold until the next release. Preliminary results show significant speed-up.

[maps90]

+1