uses exec to start serving from entrypoint

[mhrivnak]

Previously, the entrypoint script left a shell process running forever, consuming some modest resources. This change uses exec to ensure that the gpodder2go process replaces the shell process, which is a best practice for containerization.

You can see a sh process running alongside gpodder2go:

[mhrivnak@roadie ]$ podman ps
CONTAINER ID  IMAGE                            COMMAND     CREATED         STATUS         PORTS       NAMES
9ca019f13341  ghcr.io/oxtyped/gpodder2go:main              18 seconds ago  Up 18 seconds  3005/tcp    gpodder2go
[mhrivnak@roadie ]$ podman exec -it gpodder2go ps -Af
PID   USER     TIME  COMMAND
    1 root      0:00 {entrypoint.sh} /bin/sh /entrypoint.sh
   13 root      0:00 /gpodder2go serve --addr 0.0.0.0:3005
   19 root      0:00 ps -Af

after this change, the shell process is gone:

[mhrivnak@roadie ]$ podman ps
CONTAINER ID  IMAGE                  COMMAND     CREATED         STATUS         PORTS       NAMES
1c33ba12b5a5  localhost/gp2g:latest              10 seconds ago  Up 11 seconds  3005/tcp    gpodder2go
[mhrivnak@roadie gpodder2go-container]$ podman exec -it gpodder2go ps -Af
PID   USER     TIME  COMMAND
    1 root      0:00 /gpodder2go serve --addr 0.0.0.0:3005
   18 root      0:00 ps -Af