Add help text to binary

[shwoop]

The commands are not discoverable:

/workspaces/gluetun al-help ?2 ❯ ./gluetun --help                                                                                                                                                                                            root@02133880e5ee
2025-08-28T13:31:26Z ERROR command is unknown: --help
2025-08-28T13:31:26Z INFO Shutdown successful
/workspaces/gluetun al-help ?2 ❯ ./gluetun help                                                                                                                                                                                              root@02133880e5ee
2025-08-28T13:31:30Z ERROR command is unknown: help
2025-08-28T13:31:30Z INFO Shutdown successful
/workspaces/gluetun al-help ?2 ❯ ./gluetun udpate                                                                                                                                                                                            root@02133880e5ee
2025-08-28T13:31:44Z ERROR command is unknown: udpate
2025-08-28T13:31:44Z INFO Shutdown successful

I was only aware of them because I happened to snoop around the codebase.

Ironically, as we use flags, some of the commands do have help text:

/workspaces/gluetun al-help ?2 ❯ ./gluetun update --help
Usage of update:
  -all
        Update servers for all VPN providers
  -dns string
        DNS resolver address to use (default "8.8.8.8")
  -enduser
        Write results to /gluetun/servers.json (for end users)
  -ip-token string
        IP data service token (e.g. ipinfo.io) to use
  -maintainer
        Write results to ./internal/storage/servers.json to modify the program (for maintainers)
  -minratio float
        Minimum ratio of servers to find for the update to succeed (default 0.8)
  -providers string
        CSV string of VPN providers to update server data for

This PR adds new help text when a use provides -help or --help, the help text is printed by default:

/workspaces/gluetun al-help ⇡1 !1 ❯ ./gluetun-help --help
Usage: gluetun [COMMAND [OPTIONS]]

Lightweight swiss-army-knife-like VPN client to multiple VPN service providers.

Commands:
  version               Print the version of gluetun
  update                Update the VPN providers and servers
  healthcheck           Check the health of the VPN connection
  openvpnconfig         Print the OpenVPN configuration (for debugging)
  format-servers        Format the servers into a format that can be used by OpenVPN
  genkey                Generate a new OpenVPN key
/workspaces/gluetun al-help ⇡1 !1 ❯ ./gluetun-help -help
Usage: gluetun [COMMAND [OPTIONS]]

Lightweight swiss-army-knife-like VPN client to multiple VPN service providers.

Commands:
  version               Print the version of gluetun
  update                Update the VPN providers and servers
  healthcheck           Check the health of the VPN connection
  openvpnconfig         Print the OpenVPN configuration (for debugging)
  format-servers        Format the servers into a format that can be used by OpenVPN
  genkey                Generate a new OpenVPN key
/workspaces/gluetun al-help ⇡1 !1 ❯ ./gluetun-help udpate
Usage: gluetun [COMMAND [OPTIONS]]

Lightweight swiss-army-knife-like VPN client to multiple VPN service providers.

Commands:
  version               Print the version of gluetun
  update                Update the VPN providers and servers
  healthcheck           Check the health of the VPN connection
  openvpnconfig         Print the OpenVPN configuration (for debugging)
  format-servers        Format the servers into a format that can be used by OpenVPN
  genkey                Generate a new OpenVPN key
2025-08-28T13:42:52Z ERROR command is unknown: udpate
2025-08-28T13:42:52Z INFO Shutdown successful

[qdm12]

Thanks, a few adjustments to be made + eventual refactor of other code parts

[qdm12]

Actually, in order to later not forget to add a help message... it would be cool if each command be a struct implementing the interface

type Command interface {
    Run() error
    Name() string // for example "help", "genkey"
    Description() string // for example "Update the VPN servers data for some or all providers"
}

And then the help command would take a slice of all commands to print the help message? That would require to refactor a bit existing commands, so it's fine if you want to skip this comment as well.

[shwoop]

sounds good.

[shwoop]

I've made an attempt at a refactor with 2af3d40, let me know what you think.

[qdm12]

I'll review shortly, just rushing for a v3.41.0 release currently.