Two RFC/WIP series for facilitating merge conflict resolution

Hi everyone,

Last week, Duy posted an interesting RFC patch for improving merge conflict resolution by coloring the "CONFLICT' messages that are output during a merge. I have two more ideas (complementary to his) for improving merge conflict resolution experience. My two ideas are mostly independent of each other but with a couple important ties; I'll shortly respond with a short RFC/WIP series for each.

Some notes applicable to both:
  - Each has a very long cover letter, due to trying to anticipate
questions/surprises and responding to each.  It may be simpler to skip
the cover letter (or just read the up-front summary) and see if the
patches make sense,
  - I am planning to imminently start looking into my merge-recursive
rewrite[1].  One possibility is just doing these changes as part of
the new strategy...thoughts?

Elijah

[1] See part E from https://public-inbox.org/git/CABPp-BFQJZHfCJZ1qvhvVcMd-_sOfi0Fkm5PexEwzzN+Zw2akw@mail.gmail.com/; also the two RFCs I'm about to post are part C from that email.