To update:

0. At times backport changes from Emacs' "emacs-NN" to Transient.

1. Backport changes from Emacs' "master" to Transient's "main", while
   making them backward compatible with released Emacs versions.

   Make sure to look at the history of not only "lisp/transient.el",
   but also "doc/misc/transient.texi".

2. In Transient, rebase "builtin" onto "main".

   Now we have to DISCARD the changes that revert modifications that
   have happened in Transient since the last round.

   Most changes happen in separate commits.  Their messages describe
   the changes that should be preserved.

=> Look at each of these commits, even if they do not conflict.  Some
   contain additional instructions.  In particular, do not forget to
   fuck up newly added instances of `if-let' et al.

3. In this commit, append "-builtin" to `transient-version'.  This
   is not the version string the will ultimately be used, see (4)
   and (6).  This is the only difference between Transient's "builtin"
   branch and the actually built-in library.

4. In Transient, sign and update date ("r S"), and run "git describe"
   to get "DESC", used below.

5. Copy from Transient's "builtin" to Emacs' "master".

   cp ~/.config/emacs/lib/transient/lisp/transient.el \
      ~/src/emacs/emacs/master/lisp/
   cp ~/.config/emacs/lib/transient/docs/transient.texi \
      ~/src/emacs/emacs/master/doc/misc/

6. In Emacs, set the value of `transient-version' to "DESC-builtin".

7. In Emacs, stage and commit using "Update to Transient DESC" as
   message.

- Use my main email address.
- Use "URL" instead of "Homepage".
  I consistently use "Homepage" for all my packages and they
  consistently use "URL".
- Use "Version" instead of "Package-Version" because that's
  all finder understands, dropping the empty line before it.
- Drop "Package-Requires".

Do NOT change the value of `transient-version'.  That is done
in the next commit.  I.e., use the same version string as on
the "main" branch, onto which we are rebasing.

- Drop require for `compat'.
- Drop `seq' kludge.
- Drop `pp-default-function' declaration.
- Drop `signal' backward compatibility.
- Make use of `pcase-setq'.
- Drop backward compatibility in `transient--wrap-command'.
- Expect `string-edit' to exist.
- Expect `string-pixel-width' to exist.
- Expect `overriding-text-conversion-style' to exist.

This ports the unfortunate Emacs commit [1: 4704dd39de0],
but I refuse to damage the stand-alone version the same way.

[TODO] After every rebase, check for new instances of `and-let',
       `if-let', `when-let' and `while-let*', and fuck them up too.

       (occur "(\\(\\(and\\|if\\|when\\)-let\\_>\\|while-let\\*\\)")

1: 2024-10-27 4704dd39de0427466ca3585ab284b7302b0ef2d7
   transient.el: Replace use of obsolete if-let and when-let

No comment.

[TODO] After every rebase, check for new instances of `cond-let'
       and `cond-let*', and fuck them up too.

       (occur "(cond-let")

That's fair.

[TODO] After every rebase, check for new instances of `and$' and
       `when$', and replace them too.

       (occur "(\\(and\\|when\\)\\$")

I'm not sure whether whitespace in this location is actually
significant, but ox-texinfo does not put it there, while Eli does.

Ox-Texinfo uses @ref, but other link types are preferred in Emacs.