Add option to perform incremental deployment dirty checking against only local filesystem timestamps

[Scott Wells]

This is another one from chats with Mike Wannamaker. Right now dirty checking for incremental deployment compares server last mod times (timezone-adjusted) with local filesystem last mod times to determine what needs to be deployed. While this is overall more efficient than deploying everything every time, it still adds non-trivial time to the operation. An option to use only local filesystem mod files against the last successful deployment timestamp would make this considerably faster for those who can safely use that option.

[Scott Wells]

I did try to implement this at one point and it ended up yielding more false hits than would be good. Salesforce DX brings a new state tracking mechanism with it based partly on local timestamp/CRC information and partly on a new org-resident SObject. I think I might see if I can use that if the speed of deployment is still an issue, but I think that depending on only filesystem timestamps is prohibitively dangerous.