compare-config.sh

#!/bin/bash

config_list() {
	config_list=$(mktemp -t configlist)
	show_value=false
	longest_line=10

	[ "$1" == "-v" ] && show_value=true && shift

        args=("$@")
	for appi in "${!args[@]}"; do
		if $show_value; then
			heroku config --app ${args[$appi]} | sort
		else
			heroku config --app ${args[$appi]} | cut -d ':' -f 1 | sort
		fi > $config_list.$appi
		curr_longest=$(cat $config_list.$appi | awk '{ print length }' | sort -n | tail -1)
		[ "$curr_longest" -gt "$longest_line" ] && longest_line="$curr_longest"
	done

	pr -w $(($longest_line * 2)) -m -t $config_list.*
	rm $config_list.*
}

config_list $*

Usage.sh

$ compare-config -v app1 app1-staging
=== app1 Config Vars						=== app1-staging Config Vars
MMYSQL_DATABASE: mysql://staging-user:password@host.com		MMYSQL_DATABASE: mysql://staging-user:password@host.com
FEATURE_ENABLED: false						FEATURE_ENABLED: true
SERVICE_KEY_ID: AKI43DW4XFD16JONFE2Q				SERVICE_KEY_ID: IKD9ON2T999KIAIDK1XA
SERVICE_ACCESS_KEY: DFS1PGC9eICquUZjiid9sKZC9123		SERVICE_ACCESS_KEY: DFSPGC9e4ICquUZjiid9sKZC9123

$ compare-config app1 app1-staging
=== app1 Config Vars		=== app1-staging Config Vars
MMYSQL_DATABASE			MMYSQL_DATABASE
FEATURE_ENABLED			FEATURE_ENABLED
SERVICE_KEY_ID			SERVICE_KEY_ID
SERVICE_ACCESS_KEY		SERVICE_ACCESS_KEY