Setup git commit signing on macOS

A guide on how to setup git commit signing through GPG and GitHub.

1. Enable commit signing by default: git config --global commit.gpgsign true
2. add export GPG_TTY=$(tty) to your `~/.zshrc
3. Run some setup:

   brew install gpg2 gnupg pinentry-mac
   mkdir ~/.gnupg
   echo "pinentry-program $(brew --prefix)/bin/pinentry-mac" > ~/.gnupg/gpg-agent.conf
   echo 'use-agent' > ~/.gnupg/gpg.conf
   chmod 700 ~/.gnupg
   source ~/.zshrc
   git config --global gpg.program $(which gpg)
4. Generate a key
   1. gpg --full-gen-key
   2. use "RSA (sign only)" (option 4)
   3. 4096 bits long
   4. valid forever (option 0)
   5. use your git user name and email
   6. give it a passphrase (make sure to remember this!)
5. Export the key for GitHub
   1. Run gpg -K --keyid-format SHORT and copy the key id from sec rsa4096/XXXXXXX 2025-09-08 (the id is the XXXXXXX part)
   2. run gpg --armor --export <key-id> | pbcopy (pbcopy will place it in your clipboard)
   3. Go to https://github.com/settings/keys and add a new GPG key
   4. Paste into the Key textbox
6. Tell git to use your key
   1. run gpg -k
   2. Copy the fingerprint from under the pub line
   3. git config --global user.signingkey <fingerprint>
7. Make a commit, enter the passphrase from step 4.6 and save it in your keychain.