Adding GitHub password to login keychain for use with git-credential-osxkeychain:
security add-internet-password -a chasetopher -r htps -s github.com -T /Library/Developer/CommandLineTools/usr/libexec/git-core/git-credential-osxkeychain -w
security add-internet-password -a chasetopher -r htps -s gist.github.com -T /Library/Developer/CommandLineTools/usr/libexec/git-core/git-credential-osxkeychain -wDue to what I think is a bug, add-internet-password sets partition list to apple-tool: instead of apple:. (Adding the password though Keychain Access.app results in apple:)
security set-internet-password-partition-list -a chasetopher -r htps -S apple:Create new keychain: (will prompt for password) (Will be placed in ~/Library/Keychains/)
security create-keychain git.keychain(Optional) Add keychain to search list: (makes keychain appear in security list-keychains and in Keychain Access.app)
security list-keychain -d user -s login.keychain git.keychain