[PATCH 0/5] jk/send-email-sender-prompt loose ends

Here are the cleanups and refactorings split out from my jk/send-email-sender-prompt series. They can go right on master and are independent of Felipe's fc/send-email-no-sender-prompt topic.

  [1/5]: test-lib: allow negation of prerequisites

Same as before. I think this is a useful feature for the test suite (and 2/5 depends on it).

  [2/5]: t7502: factor out autoident prerequisite

Same as before. Patch 5/5 depends on it.

  [3/5]: ident: make user_ident_explicitly_given static

Same as before. Cleanup.

  [4/5]: ident: keep separate "explicit" flags for author and committer

Same as before. Cleanup. I do not know if anybody will ever care about the corner cases it fixes, so it is really just being defensive for future code.

  [5/5]: t: add tests for "git var"

Tests split out from he "git var can take multiple values" patch.

Dropped were:

  - "git var" can take multiple values. Nobody really cares about doing
    so, and it's an external interface, so we'd have to support it
    forever.

  - exporting "explicit ident" flag via "git var"; same reasoning as
    above

  - Git.pm supporting explicit ident; ditto

  - send-email prompting change; obsoleted by Felipe's patch

-Peff