Signed-off-by: Paulo Gomes <[email protected]>

internal: Expand regex to fix build [5.x]

build: raise timeouts for windows CI tests and disable CIFuzz [5.x]

This adds support for extra headers. While git has a set of 
["standard headers"] (`tree`, `parent`, `author`, `committer`, and
`encoding`), it will also support [extra headers] when serializing.

The extra headers must come after the standard ones, but they are
otherwise freetyped.

[Jujutsu] takes advantage of that to store its own identifier
(`change-id`) as an extra header.

Because signatures will cover the hash of the whole commit (standard
headers, extra headers and the message. Everything but the signature
itself), if we deserialize a commit and then `EncodeWithoutSignature` to
get back the "canonical" representation of a commit, if we don't
serialize back the extra headers, the hash will no longer match and the
signature will fail to verify.

This adds support for parsing and reencoding the extra headers from the
original commit and it's expected to fix support for Jujutsu signed
commits.

Fixes #1626

["standard headers"]: https://github.com/git/git/blob/724518f3884d8707c5f51428ba98c115818229b8/commit.c#L1450
[extra headers]: https://github.com/git/git/blob/724518f3884d8707c5f51428ba98c115818229b8/commit.c#L1690
[Jujutsu]: https://github.com/jj-vcs/jj

plumbing: support commits extra headers, support jujutsu signed commit [5.x]