[PATCH v4 0/4] Trailer readability cleanups

These patches were created while digging into the trailer code to better understand how it works, in preparation for making the trailer.{c,h} files as small as possible to make them available as a library for external users. This series was originally created as part of [1], but are sent here separately because the changes here are arguably more subjective in nature.

These patches do not add or change any features. Instead, their goal is to make the code easier to understand for new contributors (like myself), by making various cleanups and improvements. Ultimately, my hope is that with such cleanups, we are better positioned to make larger changes (especially the broader libification effort, as in "Introduce Git Standard Library" [2]).

Updates in v4 =============

 * The first 3 patches in v3 were merged into 'master'. Necessarily, those 3
   patches have been dropped.
 * Patch 4 in v3 ("trailer: rename *_DEFAULT enums to *_UNSPECIFIED") has
   been dropped, as well as Patch 9 in v3 ("trailer: make stack variable
   names match field names"). These were dropped to simplify this series for
   what I think is the more immediate, important change (see next bullet
   point).
 * Patches 5-8 in v3 are the only ones remaining in this series. They still
   solely deal with --no-divider and trailer block start/end cleanups.

Updates in v3 =============

 * Patches 4 and 6 (--no-divider and trailer block start/end cleanups) have
   been reorganized to Patches 5-8. This ended up touching commit.c in a
   minor way, but otherwise all of the changes here are cleanups and do not
   change any behavior.

Updates in v2 =============

 * Patch 1: Drop the use of a #define. Instead just use an anonymous struct
   named internal.
 * Patch 2: Don't free info out parameter inside parse_trailers(). Instead
   free it from the caller, process_trailers(). Update comment in
   parse_trailers().
 * Patch 3: Reword commit message.
 * Patch 4: Mention be3d654343 (commit: pass --no-divider to
   interpret-trailers, 2023-06-17) in commit message.
 * Added Patch 6 to make trailer_info use offsets for trailer_start and
   trailer_end (thanks to Glen Choo for the suggestion).

[1] https://lore.kernel.org/git/pull.1564.git.1691210737.gitgitgadget@gmail.com/T/#mb044012670663d8eb7a548924bbcc933bef116de [2] https://lore.kernel.org/git/20230627195251.1973421-1-calvinwan@google.com/ [3] https://lore.kernel.org/git/pull.1149.git.1677143700.gitgitgadget@gmail.com/ [4] https://lore.kernel.org/git/6b4cb31b17077181a311ca87e82464a1e2ad67dd.1686797630.git.gitgitgadget@gmail.com/ [5] https://lore.kernel.org/git/pull.1563.git.1691211879.gitgitgadget@gmail.com/T/#m0131f9829c35d8e0103ffa88f07d8e0e43dd732c

Linus Arver (4):
  commit: ignore_non_trailer computes number of bytes to ignore
  trailer: find the end of the log message
  trailer: use offsets for trailer_start/trailer_end
  trailer: only use trailer_block_* variables if trailers were found

 builtin/commit.c |   2 +-
 builtin/merge.c  |   2 +-
 commit.c         |   2 +-
 commit.h         |   4 +-
 sequencer.c      |   2 +-
 trailer.c        | 105 ++++++++++++++++++++++++++++++-----------------
 trailer.h        |  15 ++++---
 7 files changed, 83 insertions(+), 49 deletions(-)

base-commit: bcb6cae2966cc407ca1afc77413b3ef11103c175
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1563%2Flistx%2Ftrailer-libification-prep-v4
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1563/listx/trailer-libification-prep-v4
Pull-Request: https://github.com/gitgitgadget/git/pull/1563

Range-diff vs v3:

  1:  4f116d2550f <  -:  ----------- trailer: separate public from internal portion of trailer_iterator
  2:  c00f4623d0b <  -:  ----------- trailer: split process_input_file into separate pieces
  3:  f78c2345fad <  -:  ----------- trailer: split process_command_line_args into separate functions
  4:  47186a09b24 <  -:  ----------- trailer: rename *_DEFAULT enums to *_UNSPECIFIED
  5:  da52cec42e1 =  1:  4ce5cf77005 commit: ignore_non_trailer computes number of bytes to ignore
  6:  ab8a6ced143 =  2:  c904caba7e1 trailer: find the end of the log message
  7:  091805eb7d9 =  3:  796e47c1e5f trailer: use offsets for trailer_start/trailer_end
  8:  1762f78a613 =  4:  64e1bd4e4be trailer: only use trailer_block_* variables if trailers were found
  9:  a784c45ed71 <  -:  ----------- trailer: make stack variable names match field names