gitconfig

Since version 2.34 of git, it has been possible to sign commits using SSH key(s).¹ I find this handy, as it helps manage my version control workflow with just one key type. Here is a minimal example of ~/.gitconfig to set it up:

[user]
    name = Chetan Kunte
    email = <my email address>
    signingkey = ~/.ssh/<public key filename>.pub
[commit]
    gpgsign = true # sign commit(s)
[tag]
    gpgsign = true # sign tag(s)
[gpg]
    format = ssh  # use SSH key for signing commits
[gpg "ssh"]
    allowedSignersFile = ~/.ssh/allowed_signers    
[init]
    defaultBranch = master # force of habit
[core]
    editor = nvim # my preferred editor

To let GitHub know that you will use SSH key for signing commits, add the SSH public key to Settings → SSH and GPG keys → Signing keys. Copy public key as so:

pbcopy < ~/.ssh/<public key filename>.pub

To avoid “error: gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification”, add a file ~/.ssh/allowed_signers with the following contents (email, key type, public key):

<my email address> ssh-ed25519 <public key>

Replace placeholders (shown in angle brackets above) with the actual information. Test with git show --show-signature. It should show as valid.²