Here's the latest re-roll of the credential helpers series. I think this
one is probably ready to go to 'next'.

It's rebased on the latest tip of 'master' (applying it to an older
commit will get you a minor textual conflict in strbuf.c). It
incorporates the erase-safety we discussed, fixes a few commit message
typos, and tweaks the test scripts to make testing the external OS X
helper a little easier.

  [01/13]: test-lib: add test_config_global variant
  [02/13]: t5550: fix typo
  [03/13]: introduce credentials API
  [04/13]: credential: add function for parsing url components
  [05/13]: http: use credential API to get passwords
  [06/13]: credential: apply helper config
  [07/13]: credential: add credential.*.username
  [08/13]: credential: make relevance of http path configurable
  [09/13]: docs: end-user documentation for the credential subsystem
  [10/13]: credentials: add "cache" helper
  [11/13]: strbuf: add strbuf_add*_urlencode
  [12/13]: credentials: add "store" helper
  [13/13]: t: add test harness for external credential helpers

-Peff