Fix dips, nimble file handling, and gitops

[elcritch]

This PR started to work on #117 but uncovered a few other items which needed cleaned up or fixed.

Changes:

• Combine multiple ways to search for Nimble files into one place
• fixes some edge cases in handling finding Nimble files
• fixes issue with writing default config file and handling the deps cli option
• unit tests for various nimble file states (missing, ambiguous, etc)
• unit tests for parsing PkgUrl's
• merges adhoc git execs to use the gitops module, restoring logging etc
• cleanup for setting up triple-name on conflicts

[elcritch]

@Araq fixed this PR. I started tracking down another set of issues and got a broken commit mixed in here.

[Araq]

Option[string] is actually worse than string if s.len == 0 is already an errornous state. You added yet another error state on top of the one we already have. For Nimble file detection it's something like:

type
  NimbleFile = object
     results: int
     file: string # only valid if results == 1

[elcritch]

Option[string] is actually worse than string if s.len == 0 is already an errornous state. You added yet another error state on top of the one we already have.

It does introducing another possible error state, but that can be handled by ensuring the code that finds the nimble files doesn't return some(""). It's not, ideal, granted to be able to make an invalid state but it's localized to that single proc so should be easy to vet.

Mainly I found it useful in documenting elsewhere in the codebase that the Nimble file might not be found yet and that using .get will result in an easier to trace defect vs an empty string which might go unchecked.