Enable relative paths for driver_opts.device

[aiordache]

The driver options for a volume are forwarded to the docker engine unmodified (as specified in the compose file). #6343 requests support for relative paths in the 'device' option of the local driver.
This patch converts the relative paths for driver_opts.device to absolute paths (only for a local driver and bind mount option).

docker-compose.yml

version: '3.8'
services:
  app:
    image: nginx
    volumes:
      - vol:/test
volumes:
  vol:
    driver_opts:
      type: none
      o: bind
      device: .

$ pwd
/home/anca/compose/test
$ ls
docker-compose.yml

$ docker-compose up -d

$ docker volume ls
DRIVER              VOLUME NAME
local               test_vol

$ docker volume inspect test_vol
[
    {
        "CreatedAt": "2020-09-03T14:52:50+02:00",
        "Driver": "local",
        "Labels": {
            "com.docker.compose.project": "test",
            "com.docker.compose.version": "1.28.0dev",
            "com.docker.compose.volume": "vol"
        },
        "Mountpoint": "/home/anca/.local/docker/volumes/test_vol/_data",
        "Name": "test_vol",
        "Options": {
            "device": "/home/anca/compose/test",
            "o": "bind",
            "type": "none"
        },
        "Scope": "local"
    }
]

$ docker exec -t  test_app_1 sh -c "ls /test"
docker-compose.yml

Resolves #6343

[ulyssessouza]

nit:

Suggested change

	if o and o == 'bind' and device:
	if o == 'bind' and device:

[ulyssessouza]

LGTM

[maaarghk]

Please see #7856, I believe this introduced a BC break on a point release. The check for existing volumes with different "driver_opts.device" value needs updated to check resolved path returned from the daemon.

[djherbis]

@aiordache I think there's another related regression affecting me because of this.

I execute docker-compose on Windows, with a remote docker host on Linux. The expansion/abs path transformation ends up converting Linux absolute paths (like /path/from/root), into Windows-style paths (like C:/path/from/root), which ends up as an invalid path on the remote filesystem (and caused my volumes to report that the 'device' changed even though I haven't changed my docker-compose file in years).

Anything we can do to fix this? Maybe don't try to normalize these paths when you're not talking to a local docker daemon, since the filesystem is totally different?