docker-rundev

#!/usr/bin/python3

import argparse
from contextlib import contextmanager
from subprocess import call, check_call, SubprocessError
import re
import os
import sys
import tempfile

def die(fmt, *k):
    sys.stderr.write("error: %s\n" % (fmt % k))
    sys.exit(1)

def shellquote(cmd):
    if isinstance(cmd, str):
        return cmd if re.match(r"[a-zA-Z0-9_,.+=:/-]+\Z", cmd) else repr(cmd)
    else:
        assert all(isinstance(x, str) for x in cmd)
        return " ".join(map(shellquote, cmd))


@contextmanager
def overlay(source):
    assert ":" not in source
    assert "=" not in source

    with tempfile.TemporaryDirectory() as tmp:
        diff = os.path.join(tmp, "diff")
        mnt  = os.path.join(tmp, "mnt")
        os.mkdir(diff)
        os.mkdir(mnt)
        try:
            check_call(["unionfs-fuse", "-o", "cow,allow_root", "%s=RW:%s=RO" % (diff, source), mnt])
            yield mnt
        finally:
            call(["fusermount", "-u", mnt])


def run_docker(args, source):
    cmd = ["docker", "run", "--rm",
        "-w", "/source",
        "-v", "/tmp",
        "-v", "%s:/source" % source]

    for name in "target", "cache":
        path = getattr(args, name)
        if path:
            os.path.isdir(path) or os.makedirs(path)
            cmd.extend(("-v", "%s:/%s:rw" % (os.path.realpath(path), name)))

    if args.root:
        cmd.extend(("-u", "0:0"))
    else:
        cmd.extend(("-u", "%d:%d" % (os.getuid(), os.getgid())))
        for group in os.getgroups():
            cmd.extend(("--group-add", str(group)))

    if not os.path.isdir(args.source):
        die("source must be a directory: %r", args.source)

    cmd.extend(args.extra)
    print(shellquote(cmd))
    return call(cmd)


def main():
    parser = argparse.ArgumentParser("docker-rundev",
            usage="docker-rundev [ OPTIONS ] [ -- DOCKER_OPTIONS ] ...")
    parser.add_argument("extra", metavar="...", nargs=argparse.REMAINDER,
            help="arguments to be provided to 'docker run'")
    parser.add_argument("-s", "--source", default=".",
            help="host path of the source dir (mounted as /source with an overlay)")
    parser.add_argument("-t", "--target",
            help="host path of the target dir (mounted as /target)")
    parser.add_argument("-c", "--cache",
            help="host path of the cache dir (mounted as /cache)")

    parser.add_argument("-r", "--root", action="store_true",
            help="run container as root")
    
    args = parser.parse_args()
    if args.extra and args.extra[0] == "--":
        args.extra.pop(0)

    try:
        with overlay(args.source) as source_mnt:
            return run_docker(args, source_mnt)
    except SubprocessError as e:
        die("%s", e)

if __name__ == "__main__":
    sys.exit(main())