podman generate systemd should only prepend separator when prefix is non-empty

[lovette]

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind bug

Description

When the --container-prefix and/or --pod-prefix options to podman generate systemd are set to empty string, the default --separator should not be prepended. It creates filenames that begin with a hyphen, which are frustrating to deal with.

$ podman generate systemd --new --name --files --pod-prefix='' --container-prefix='' mariadb-pod
-mariadb-pod.service
-mariadb.service

$ ls *.service
ls: invalid option -- '-'

$ ls -- *.service
-mariadb-pod.service  -mariadb.service

Of course, you can workaround this by also setting the --separator to an empty string.

$ podman generate systemd --new --name --files --pod-prefix='' --container-prefix='' --separator='' mariadb-pod
mariadb-pod.service
mariadb.service

Steps to reproduce the issue:

$ podman generate systemd --new --name --files --pod-prefix='' --container-prefix='' mariadb-pod

Describe the results you received:

% ls --
-mariadb-pod.service -mariadb.service

Describe the results you expected:

$ ls
mariadb-pod.service mariadb.service

Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version:

Client:       Podman Engine
Version:      4.0.0-rc5
API Version:  4.0.0-rc5
Go Version:   go1.17.5

Built:      Sat Feb 12 01:12:41 2022
OS/Arch:    linux/amd64

Output of podman info --debug:

host:
	arch: amd64
	buildahVersion: 1.24.1
	cgroupControllers:
	- cpuset
	- cpu
	- io
	- memory
	- hugetlb
	- pids
	- rdma
	- misc
	cgroupManager: systemd
	cgroupVersion: v2
	conmon:
		package: conmon-2.1.0-1.el9.x86_64
		path: /usr/bin/conmon
		version: 'conmon version 2.1.0, commit: 8ef5de138efb6f0aad657082cdea22cf037792cb'
	cpus: 2
	distribution:
		distribution: '"centos"'
		version: "9"
	eventLogger: journald
	hostname: dd-grogu-dev
	idMappings:
		gidmap: null
		uidmap: null
 kernel: 5.14.0-47.el9.x86_64
	linkmode: dynamic
	logDriver: journald
	memFree: 2074648576
	memTotal: 4073611264
	networkBackend: netavark
	ociRuntime:
		name: crun
		package: crun-1.4.2-1.el9.x86_64
		path: /usr/bin/crun
		version: |-
			crun version 1.4.2
			commit: f6fbc8f840df1a414f31a60953ae514fa497c748
			spec: 1.0.0
			+SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +YAJL
	os: linux
	remoteSocket:
		exists: true
		path: /run/podman/podman.sock
	security:
		apparmorEnabled: false
		capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
		rootless: false
		seccompEnabled: true
		seccompProfilePath: /usr/share/containers/seccomp.json
		selinuxEnabled: true
	serviceIsRemote: false
	slirp4netns:
		executable: /bin/slirp4netns
		package: slirp4netns-1.1.8-3.el9.x86_64
		version: |-
			slirp4netns version 1.1.8
			commit: d361001f495417b880f20329121e3aa431a8f90f
			libslirp: 4.4.0
			SLIRP_CONFIG_VERSION_MAX: 3
			libseccomp: 2.5.2
	swapFree: 2146430976
	swapTotal: 2147479552
	uptime: 50h 19m 42.78s (Approximately 2.08 days)
plugins:
 log:
	- k8s-file
	- none
	- passthrough
	- journald
	network:
	- bridge
	- macvlan
	volume:
	- local
registries:
	search:
	- registry.fedoraproject.org
	- registry.access.redhat.com
	- docker.io
	- quay.io
store:
	configFile: /etc/containers/storage.conf
	containerStore:
		number: 15
		paused: 0
		running: 15
		stopped: 0
	graphDriverName: overlay
	graphOptions:
		overlay.mountopt: nodev,metacopy=on
	graphRoot: /var/lib/containers/storage
	graphStatus:
		Backing Filesystem: xfs
		Native Overlay Diff: "false"
		Supports d_type: "true"
		Using metacopy: "true"
	imageCopyTmpDir: /var/tmp
	imageStore:
		number: 24
	runRoot: /run/containers/storage
	volumePath: /var/lib/containers/storage/volumes
version:
	APIVersion: 4.0.0-rc5
	Built: 1644628361
	BuiltTime: Sat Feb 12 01:12:41 2022
	GitCommit: ""
	GoVersion: go1.17.5
	OsArch: linux/amd64
	Version: 4.0.0-rc5

Package info (e.g. output of rpm -q podman or apt list podman):

podman-4.0.0-0.7.rc5.el9.x86_64

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide? (https://github.com/containers/podman/blob/main/troubleshooting.md)

Yes

Additional environment details (AWS, VirtualBox, physical, etc.):

Running on CentOS 9 Stream in a VMware Fusion VM.

[Luap99]

I think using --separator="" is the best solution, removing the default separator might cause other problems. What if I only use --pod-prefix=''?

[lovette]

The options all make sense as they stand. I just think the given separator should only be prepended if the relevant prefix is non-empty. Filenames starting with a hyphen is an annoying footgun 😁

An alternate wish would be to have --no-pod-prefix and --no-container-prefix options. And personally, I'm a suffix person, so corresponding --suffix options would be useful too.

[Luap99]

Given the option is called separator and there is nothing to separate in this case it would make sense to this.
Interested in opening a PR?

[lovette]

Happily if I could, but I don't know Go 😁