gpg.ssh.defaultKeyCommand docs bug?

[matthew sporleder <msporleder@gmail.com>]

https://git-scm.com/docs/git-config#Documentation/git-config.txt-gpgsshdefaultKeyCommand

This command that will be run when user.signingkey is not set and a
ssh signature is requested. On successful exit a valid ssh public key
prefixed with key:: is expected in the first line of its output. This
allows for a script doing a dynamic lookup of the correct public key
when it is impractical to statically configure user.signingKey. For
example when keys or SSH Certificates are rotated frequently or
selection of the right key depends on external factors unknown to git.

---

The command does not actually work (for me, git version 2.42.0) with
key:: prefixed.

It only works if I cat the public key as-is.

I only figured this out because the docs previously said it took the
format of ssh-add -L, which also doesn't not contain key::.

I am using this script for my "dynamic" key discovery:
#!/bin/sh
f=$(ssh -G $(git remote get-url $(git remote|head -1)|awk -F':' '{
print $1 }') |grep -E '^identityfile'|sed 's#^identityfile ##g')
cat $(eval realpath ${f}.pub)

Thanks,
Matt