[PATCH v2 0/6] allow non-trailers and multiple-line trailers

Thanks, Peff, for the pointer to list.h. Using list.h does simplify the code by a similar amount to switching it to a singly-linked list, so I have done that (replacing my earlier "trailer: use singly-linked list, not doubly" patch). Another advantage is that I no longer need to change the algorithm, making for a smaller patch.

(There are some quirks resulting from list.h implementing a circular list, like needing to pass "head" as a sentinel when iterating from the middle of the list, but those are minor, and my original singly-linked list implementation had quirks too anyway like needing to pass a pointer to the next pointer.)

Updates:
 (-> 1/6)
 - Added separate patch for const correctness changes
 (1/5 -> 2/6)
 - Dropped singly-linked list patch, instead replacing existing
   doubly-linked list implementation with list.h
 (5/5 -> 6/6)
 - Used "char *" instead of "struct strbuf"
 - Modified test slightly to test whitespace at beginning of line

Jonathan Tan (6):
  trailer: improve const correctness
  trailer: use list.h for doubly-linked list
  trailer: streamline trailer item create and add
  trailer: make args have their own struct
  trailer: allow non-trailers in trailer block
  trailer: support values folded to multiple lines

 Documentation/git-interpret-trailers.txt |  10 +-
 t/t7513-interpret-trailers.sh            | 174 ++++++++++
 trailer.c                                | 538 +++++++++++++++----------------
 3 files changed, 444 insertions(+), 278 deletions(-)