[PATCH v7 0/2] Add mailmap mechanism in cat-file options

Thanks a ton Christian and Ævar for the review :) I have made the suggested changes in v7.

= Description

At present, `git-cat-file` command with `--batch-check` and `-s` options does not complain when `--use-mailmap` option is given. The latter option is just ignored. Instead, for commit/tag objects, the command should compute the size of the object after replacing the idents and report it. So, this patch series makes `-s` and `--batch-check` options of `git-cat-file` honor mailmap when used with `--use-mailmap` option.

In this patch series we didn't want to change that '%(objectsize)' always shows the size of the original object even when `--use-mailmap` is set because first we have the long term plan to unify how the formats for `git cat-file` and other commands works. And second existing formats like the "pretty formats" used by `git log` have different options for fields respecting mailmap or not respecting it (%an is for author name while %aN for author name respecting mailmap).

I would like to thank my mentors, Christian Couder and John Cai, for all of their help! Looking forward to the reviews!

= Patch Organization

- The first patch makes `-s` option to return updated size of the
  <commit/tag> object, when combined with `--use-mailmap` option, after
  replacing the idents using the mailmap mechanism.
- The second patch makes `--batch-check` option to return updated size of
  the <commit/tag> object, when combined with `--use-mailmap` option,
  after replacing the idents using the mailmap mechanism.

= Changes in v5

- The patch series which improves the documentation for `-s`, `--batch`,
  `--batch-check` and `--batch-command` is again part of this patch
  series with patch 3/3 squashed into patches 1/3 and 2/3 as suggested
  by Junio, Taylor and Christian. The doc patch series was perviously
  sent independently for improving the documentation of git cat-file
  options:
  https://lore.kernel.org/git/20221029092513.73982-1-siddharthasthana31@gmail.com/

- Improve the tests according to run under SHA-256 mode.

= Changes in v6

- Improve the tests so it doesn't break under macOS.

= Changes in v7

- Used `repo_read_object_file` instead of `read_object_file` because we
  have been trying to migrate away from these, and new code should use
  the non-macro variants.
- Improve the documentation of patch series.

Siddharth Asthana (2):
  cat-file: add mailmap support to -s option
  cat-file: add mailmap support to --batch-check option

 Documentation/git-cat-file.txt | 53 +++++++++++++++++++--------
 builtin/cat-file.c             | 28 +++++++++++++++
 t/t4203-mailmap.sh             | 65 ++++++++++++++++++++++++++++++++++
 3 files changed, 132 insertions(+), 14 deletions(-)

Range-diff against v6:
1:  7f20f45183 = 1:  2097544b2d cat-file: add mailmap support to -s option
2:  971f38e064 ! 2:  8305148718 cat-file: add mailmap support to --batch-check option
    @@ Commit message
     
         2. Make one call to `oid_object_info_extended()` to get the type of the
            object. Then, if the object type is either of commit or tag, make a
    -       call to `read_object_file()` to read the contents of the object.
    +       call to `repo_read_object_file()` to read the contents of the object.
     
         I benchmarked the following command with both the above approaches and
         compared against the current implementation where `--use-mailmap`
    @@ Documentation/git-cat-file.txt: OPTIONS
     -	also need to specify the path, separated by whitespace.  See the
     -	section `BATCH OUTPUT` below for details.
     +	on stdin. May not be combined with any other options or arguments
    -+	except --textconv, --filters, or --use-mailmap.
    ++	except `--textconv`, `--filters`, or `--use-mailmap`.
     +	+
     +	* When used with `--textconv` or `--filters`, the input lines
     +	  must specify the path, separated by whitespace. See the section
    @@ Documentation/git-cat-file.txt: OPTIONS
     -	need to specify the path, separated by whitespace.  See the
     -	section `BATCH OUTPUT` below for details.
     +	Print object information for each object provided on stdin. May not be
    -+	combined with any other options or arguments except --textconv, --filters
    -+	or --use-mailmap.
    ++	combined with any other options or arguments except `--textconv`, `--filters`
    ++	or `--use-mailmap`.
     +	+
     +	* When used with `--textconv` or `--filters`, the input lines must
     +	 specify the path, separated by whitespace. See the section
    @@ builtin/cat-file.c: static void batch_object_write(const char *obj_name,
     +			size_t s = data->size;
     +			char *buf = NULL;
     +
    -+			buf = read_object_file(&data->oid, &data->type, &data->size);
    ++			buf = repo_read_object_file(the_repository, &data->oid, &data->type,
    ++						    &data->size);
     +			buf = replace_idents_using_mailmap(buf, &s);
     +			data->size = cast_size_t_to_ulong(s);
     +