Add the Mozilla Public License (MPL) v2.0 header to every source file in a directory. Apache's license-eye does this already, but its formatting of comments isn't perfect, e.g. no newline after the header comment.

add_mpl_header.py

#!/usr/bin/env python3

from collections import namedtuple
from ctypes import Union
import os
import argparse
from fileinput import FileInput
import textwrap

parser = argparse.ArgumentParser()
parser.add_argument("--holder", required=True)
parser.add_argument("--year", required=True)
parser.add_argument("dir")
args = parser.parse_args()

excluded_dirnames = [
    'build',
]


Header = namedtuple('Header', ['comment', 'file_extensions'])
# DISCLAIMER: These are standard Exhibit A headers, but with https URLs
headers = [
    Header(
        comment=
        f"""\
            # Copyright (c) {args.year} {args.holder}
            #
            # This Source Code Form is subject to the terms of the Mozilla Public
            # License, v. 2.0. If a copy of the MPL was not distributed with this
            # file, You can obtain one at https://mozilla.org/MPL/2.0/.\
        """,
        file_extensions=[
            'py',
            'yaml',
            'yml',
            'sh',
            'Dockerfile',
        ],
    ),
    Header(
        comment=
        f"""\
            /*
             * Copyright (c) {args.year} {args.holder}
             *
             * This Source Code Form is subject to the terms of the Mozilla Public
             * License, v. 2.0. If a copy of the MPL was not distributed with this
             * file, You can obtain one at https://mozilla.org/MPL/2.0/.
             */\
        """,
        file_extensions=[
            'java',
            'kt',
            'kts',
            'gradle',
            'groovy',
            'gvy',
        ],
    ),
]


def prepend_comment(comment, filepath):
    # Trim common indents in multi-line string
    comment = textwrap.dedent(comment)
    if os.stat(filepath).st_size == 0:
        with open(filepath, 'w') as file:
            file.write(f"{comment}\n")
            return
    with FileInput(filepath, inplace=True) as file:
        header_line = 1
        for line in file:
            if file.lineno() == header_line:
                # Always scan line before deciding to print comment
                if line.startswith("#!"):
                    # Print shebang and leave comment for the next round
                    print(line)
                    header_line = 2
                    continue
                else:
                    print(comment)
                    if not line.startswith('\n'):
                        # Ensure there's 1 blank line between comment and first source line
                        print('')
            print(line, end='')


def decide_header_comment(filename: str) -> str:
    if filename in __file__:
        # In case this script is editing its own directory
        return None
    file_extension = filename.split('.')[-1]
    for header in headers:
        if file_extension in header.file_extensions:
            return header.comment
    return None


for root, dirnames, filenames in os.walk(args.dir):
    for exclude in [d for d in dirnames if d in excluded_dirnames]:
        dirnames.remove(exclude)
    for name in filenames:
        comment = decide_header_comment(name)
        if comment is None:
            continue
        path = os.path.join(root, name)
        print("Editing", path)
        prepend_comment(comment, path)