heroku-buildpack-uml/bin/fix_procfile

#!/usr/bin/env python3
import sys, shlex

procfile_path = sys.argv[1]

lines = []

with open(procfile_path) as file:
    for line in file:
        if ":" in line:
            type, cmd = line.split(':', 1)
            lines.append(type+': /app/.uml/uml_run '+shlex.quote('cd /app; '+cmd.strip())+'\n')
        else:
            lines.append(line)

with open(procfile_path, 'w') as file:
    file.writelines(lines)