[PATCH v3 0/5] date.[ch] API: split from cache.h, add API docs, stop leaking memory

Fix memory leaks in the date.[ch] API, in preparation for larger changes to make the revision walking API stop leaking memory.

This is small re-roll of v2 to address Junio's feedback on that version. For v2 see: https://lore.kernel.org/git/cover-v2-0.5-00000000000-20220204T235143Z-avarab@gmail.com/

This is a documentation and commit-message only update. As explained below I think it makes sense to punt on the "builtin/blame.c" leak, and to keep 2/5 as-is with date.h not included in cache.h, but those things are now all rationalized in the commit message. Thanks for the review Junio!

Ævar Arnfjörð Bjarmason (5):
  cache.h: remove always unused show_date_human() declaration
  date API: create a date.h, split from cache.h
  date API: provide and use a DATE_MODE_INIT
  date API: add basic API docs
  date API: add and use a date_mode_release()

 archive-zip.c         |  1 +
 builtin/am.c          |  1 +
 builtin/commit.c      |  1 +
 builtin/fast-import.c |  1 +
 builtin/show-branch.c |  1 +
 builtin/tag.c         |  1 +
 cache.h               | 50 -----------------------------
 config.c              |  1 +
 date.c                |  9 ++++--
 date.h                | 74 +++++++++++++++++++++++++++++++++++++++++++
 http-backend.c        |  1 +
 ident.c               |  1 +
 object-name.c         |  1 +
 pretty.h              | 10 ++++++
 ref-filter.c          |  3 +-
 reflog-walk.h         |  1 +
 refs.c                |  1 +
 strbuf.c              |  1 +
 t/helper/test-date.c  |  5 ++-
 t/t0006-date.sh       |  2 ++
 20 files changed, 112 insertions(+), 54 deletions(-)
 create mode 100644 date.h

Range-diff against v2:
1:  fb21bd7b2c5 = 1:  97746d97810 cache.h: remove always unused show_date_human() declaration
2:  96c904d0b9a ! 2:  f73aa601e95 date API: create a date.h, split from cache.h
    @@ Commit message
         use the "DATE_MODE()" macro we now define in date.h, let's have them
         include it.
     
    +    We could simply include this new header in "cache.h", but as this
    +    change shows these functions weren't common enough to warrant
    +    including in it in the first place. By moving them out of cache.h
    +    changes to this API will no longer cause a (mostly) full re-build of
    +    the project when "make" is run.
    +
         Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
     
      ## archive-zip.c ##
3:  9ef003a83bd = 3:  764147e90e1 date API: provide and use a DATE_MODE_INIT
4:  3f70b1aa4c5 ! 4:  5c244960133 date API: add basic API docs
    @@ date.h: struct date_mode {
      struct date_mode *date_mode_from_type(enum date_mode_type type);
      
     +/**
    -+ * Show the date given an initialized "struct date_mode" (usually from
    -+ * the DATE_MODE() macro).
    ++ * Format <'time', 'timezone'> into static memory according to 'mode'
    ++ * and return it. The mode is an initialized "struct date_mode"
    ++ * (usually from the DATE_MODE() macro).
     + */
      const char *show_date(timestamp_t time, int timezone, const struct date_mode *mode);
     +
5:  60dbadacb16 ! 5:  b1ee9a30913 date API: add and use a date_mode_release()
    @@ Commit message
         release_revisions() in "revision.c", as they have to do with leaks via
         "struct rev_info".
     
    +    There is also a leak in "builtin/blame.c" due to its call to
    +    parse_date_format() to parse the "blame.date" configuration. However
    +    as it declares a file-level "static struct date_mode blame_date_mode"
    +    to track the data, LSAN will not report it as a leak. It's possible to
    +    get valgrind(1) to complain about it with e.g.:
    +
    +        valgrind --leak-check=full --show-leak-kinds=all ./git -P -c blame.date=format:%Y blame README.md
    +
    +    But let's focus on things LSAN complains about, and are thus
    +    observable with "TEST_PASSES_SANITIZE_LEAK=true". We should get to
    +    fixing memory leaks in "builtin/blame.c", but as doing so would
    +    require some re-arrangement of cmd_blame() let's leave it for some
    +    other time.
    +
         Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
     
      ## date.c ##