git-idm

#!/bin/bash
#Created by Sam Gleske
#License: MIT
#Project URL: https://github.com/samrocketman/git-identity-manager

version='0.6'

if ! git --version | awk 'BEGIN { FS="." }; $2 < 10 { exit(1) }'; then
    echo 'WARNING: "git --version" is older than Git 2.10.  git-idm will have unexpected behavior.' >&2
fi

function echo_version() {
    echo "git idm v${version}" >&2
}

function usage() {
    cat >&2 <<EOF
Git identity manager (git idm).  It allows you to switch between git identities
for user, name, and SSH private key used for authoring and publishing git
commits.

Synopsis: git ${0##*/git-} COMMAND [ID] [OPTIONS]

Example usage:

    git ${0##*/git-} add jcool --name "Joe Cool" --email "joe@example.com" --key ~/.ssh/id_rsa
    git ${0##*/git-} list
    git ${0##*/git-} use jcool
    git ${0##*/git-} remove jcool

Commands:

       active - Display the identity currently used by git idm.
          add - Add or update an identity.  --name, --email, and --key are
                required when adding an identity for the first time only.
         list - List identites.  ls for short.
       remove - Remove a single identity or all identities.  rm for short.
    uninstall - Removes all git idm data from global gitconfig.  All git idm
                identities will be removed.  This will not affect settings not
                related to git idm.
          use - Actively use an identity for git authorship and publishing.
      version - Output version information.

Command options:

    active has no options
    add:
                               ID - The first argument is the identity ID.
                      --name NAME - Name of the associated identity.
                    --email EMAIL - Email of the associated identity.
                    --key SSH_KEY - SSH private key of the associated identity.
        --ssh-command SSH_COMMAND - Customize the SSH command ignoring --key.
    list has no options.
    use:
        ID - Identity to activate.
    remove:
        ID - Remove the identity.  If ID is "all" then all identities will be
             removed.
    uninstall has no options
EOF
    echo_version
    exit 1
}

function print_identities() {
    awk '
    BEGIN {
        FS="."
    }
    $1 == "gitidm" && section != $2 {
        section=$2
        print $2
    }
    $1 == "gitidm" {
        output="    "$3
        for(i = 4; i <= NF; i++) {
            output=output"."$i
        }
        print output
    }
    '
}

function run_command() {
    case $4 in
        user.name|user.email|core.sshCommand)
            echo "$1 $2 $3 $4 \"$5\""
            ;;
        *)
            echo "$*"
            ;;
    esac
    "$@"
}

function identity_exists() {
    git config --global --list | grep "^gitidm\\.${id}\\." &> /dev/null
}

function check_ssh_agent() {
    if ! ssh-add -l | grep -F -- "$1" &> /dev/null; then
        echo "WARNING: $1 has not been added to ssh-agent.  To fix run: ssh-add '$1'" >&2
    fi
}

#################
# OPTION HANDLING
#################
# command (required in all cases)
comm="$1"
shift
# identity ID (optional in some cases)
id="$1"
shift
NAME=""
EMAIL=""
SSH_KEY=""
SSH_COMMAND=""
if [ -z "${comm}" ]; then
    echo "ERROR: command not specified.  See 'git idm help'."
    exit 1
fi
if [[ "${comm}" = "-h" || "${id}" = "-h" ]]; then
    usage
fi
if [[ "${comm}" = "-v" || "${id}" = "-v" || "${comm}" = "--version" || "${id}" = "--version" ]]; then
    echo_version
    exit
fi
# parse additional arguments
while [[ $# -gt 0 ]]; do
    case "$1" in
        --name)
            NAME="$2"
            shift 2
            ;;
        --email)
            EMAIL="$2"
            shift 2
            ;;
        --key)
            if [ ! -r "$2" ]; then
                echo "ERROR: Private key ${2} does not exist." >&2
                exit 1
            fi
            if [ -n "${SSH_COMMAND}" ]; then
                echo 'ERROR: --key conflicts with --ssh-command.  Use one or the other.' >&2
                exit 1
            fi
            SSH_KEY="$2"
            SSH_COMMAND="ssh -i $2 -o IdentitiesOnly=yes -F /dev/null"
            shift 2
            ;;
        --ssh-command)
            if [ -n "${SSH_KEY}" ]; then
                echo 'ERROR: --ssh-command conflicts with --key.  Use one or the other.' >&2
                exit 1
            fi
            SSH_COMMAND="$2"
            shift 2
            ;;
        -h)
            usage
            ;;
        --version|-v)
            echo_version
            exit
            ;;
        *)
            echo "ERROR: option $1 not recognized.  See 'git idm help'." >&2
            exit 1
            ;;
    esac
done

###################
# RUN COMMAND LOGIC
###################
case "${comm}" in
    active)
        ACTIVE_ID="$(git config --global --get user.activeidm)"
        NAME="$(git config --global --get gitidm."${ACTIVE_ID}".name)"
        REAL_NAME="$(git config --global --get user.name)"
        EMAIL="$(git config --global --get gitidm."${ACTIVE_ID}".email)"
        REAL_EMAIL="$(git config --global --get user.email)"
        SSH_COMMAND="$(git config --global --get gitidm."${ACTIVE_ID}".sshCommand)"
        REAL_SSH_COMMAND="$(git config --global --get core.sshCommand)"
        SSH_KEY="$(git config --global --get gitidm."${ACTIVE_ID}".sshKey)"
        DISCREPENCY=false
        if [ -n "${ACTIVE_ID}" ]; then
            git config --global --list | grep "^gitidm\\.${ACTIVE_ID}\\." | print_identities
            check_ssh_agent "${SSH_KEY}"
            if [ ! "${NAME}" = "${REAL_NAME}" ]; then
                echo "WARNING: user.name '${REAL_NAME}' does not match the one used by the identity." >&2
                DISCREPENCY=true
            fi
            if [ ! "${EMAIL}" = "${REAL_EMAIL}" ]; then
                echo "WARNING: user.email '${REAL_EMAIL}' does not match the one used by the identity." >&2
                DISCREPENCY=true
            fi
            if [ ! "${SSH_COMMAND}" = "${REAL_SSH_COMMAND}" ]; then
                echo "WARNING: core.sshCommand '${REAL_SSH_COMMAND}' does not match the one used by the identity." >&2
                DISCREPENCY=true
            fi
            if [ "${DISCREPENCY}" = true ]; then
                echo "ERROR: found above discrepencies with identity.  To fix run 'git idm use ${ACTIVE_ID}'." >&2
                exit 1
            fi
        else
            echo 'No identites are active.'
        fi
        ;;
    add)
        if [ "${id}" = all ]; then
            echo 'ERROR: May not add an identity with the ID "all".  This is a reserved ID.' >&2
            exit 1
        fi
        if ! identity_exists && [[ -z "${NAME}" || -z "${EMAIL}" || ( -z "${SSH_KEY}" && -z "${SSH_COMMAND}" ) ]]; then
            echo 'ERROR: options --name, --email, and --key or --ssh-command are required when adding an identity for the first time.' >&2
            exit 1
        fi
        if [ -n "${NAME}" ]; then
            git config --global gitidm."${id}".name "${NAME}"
        fi
        if [ -n "${EMAIL}" ]; then
            git config --global gitidm."${id}".email "${EMAIL}"
        fi
        if [ -n "${SSH_KEY}" ]; then
            git config --global gitidm."${id}".sshKey "${SSH_KEY}"
            check_ssh_agent "${SSH_KEY}"
        fi
        if [ -n "${SSH_COMMAND}" ]; then
            git config --global gitidm."${id}".sshCommand "${SSH_COMMAND}"
        fi
        ;;
    help)
        usage
        ;;
    list|ls)
        git config --global --list | print_identities
        ;;
    remove|rm)
        if [ -z "${id}" ]; then
            echo 'ERROR: No identity selected for removal.'
            exit 1
        fi
        if [ "${id}" = all ]; then
            git config --global --list |
            awk '
            BEGIN {
                FS="."
            }
            $1 == "gitidm" && section != $2 {
                section=$2
                print $2
            }
            ' |
            while read -r x; do
                "$0" remove "$x"
            done
        else
            git config --global --remove-section gitidm."${id}"
            echo "Removed identity ${id}."
        fi
        ;;
    uninstall)
        "$0" remove all
        #throw away the exit code because we don't care
        run_command git config --global --unset user.activeidm || true
        echo 'To complete uninstallation run the following command:' >&2
        echo "rm \"$0\"" >&2
        ;;
    use)
        if ! identity_exists; then
            echo "ERROR: Identity ${id} does not exist.  See 'git idm list' or 'git idm help'." >&2
            exit 1
        fi
        NAME="$(git config --global --get gitidm."${id}".name)"
        EMAIL="$(git config --global --get gitidm."${id}".email)"
        SSH_COMMAND="$(git config --global --get gitidm."${id}".sshCommand)"
        SSH_KEY="$(git config --global --get gitidm."${id}".sshKey)"
        if [ -n "${NAME}" ]; then
            run_command git config --global user.name "${NAME}"
        fi
        if [ -n "${EMAIL}" ]; then
            run_command git config --global user.email "${EMAIL}"
        fi
        if [ -n "${SSH_COMMAND}" ]; then
            run_command git config --global core.sshCommand "${SSH_COMMAND}"
        fi
        run_command git config --global user.activeidm "${id}"
        if [ -n "${SSH_KEY}" ]; then
            check_ssh_agent "${SSH_KEY}"
        fi
        ;;
    version)
        echo_version
        ;;
    *)
        echo "ERROR: Command ${comm} not found.  See 'git idm help'." >&2
        exit 1
        ;;
esac