Even though the cat-file command with `--batch-check` option does not
complain when `--use-mailmap` option is given, the latter option is
ignored. Compute the size of the object after replacing the idents and
report it instead.
In order to make `--batch-check` option honour the mailmap mechanism we
have to read the contents of the commit/tag object.
There were two ways to do it:
1. Make two calls to `oid_object_info_extended()`. If `--use-mailmap`
option is given, the first call will get us the type of the object
and second call will only be made if the object type is either a
commit or tag to get the contents of the object.
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 `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`
option is ignored:
`git cat-file --use-mailmap --batch-all-objects --batch-check --buffer
--unordered`
The results can be summarized as follows:
Time (mean ± σ)
default 827.7 ms ± 104.8 ms
first approach 6.197 s ± 0.093 s
second approach 1.975 s ± 0.217 s
Since, the second approach is faster than the first one, I implemented
it in this patch.
The command git cat-file can now use the mailmap mechanism to replace
idents with canonical versions for commit and tag objects. There are
several options like `--batch`, `--batch-check` and `--batch-command`
that can be combined with `--use-mailmap`. But the documentation for
`--batch`, `--batch-check` and `--batch-command` doesn't say so. This
patch fixes that documentation.
Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: John Cai <johncai86@gmail.com>
Helped-by: Taylor Blau <me@ttaylorr.com>
Helped-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Siddharth Asthana <siddharthasthana31@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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