sync: Sync .mailmap entries

The kernel repository has a .mailmap file to remap author names and
email addresses to their desired format in Git logs (for details, see
gitmailmap documentation [0]). Alas, this is only visible for author
information when looking at the logs locally, as GitHub does not support
mailmaps at the moment [1].

This commit adds a .mailmap file for libbpf, automatically generated
from the kernel's version. The script to generate the .mailmap is added,
too: it works by grepping email addresses from authors in the
repository, and collecting all lines ending with this address in the
kernel's .mailmap - in other words, all lines where this address is used
as a pattern for a remapping.

To keep the .mailmap up-to-date, add a call to the script to
sync-kernel.sh.

[0] https://git-scm.com/docs/gitmailmap
[1] https://github.com/orgs/community/discussions/22518

Signed-off-by: Quentin Monnet <qmo@kernel.org>

scripts/sync-kernel.sh

@@ -352,4 +352,10 @@ else
 	esac
 fi
 
+echo "Regenerating .mailmap..."
+cd_to "${LINUX_REPO}"
+git checkout "${TIP_SYM_REF}"
+cd_to "${LIBBPF_REPO}"
+"${LIBBPF_REPO}"/scripts/mailmap-update.sh "${LIBBPF_REPO}" "${LINUX_REPO}"
+
 cleanup