podman-compose does not support mounting external secrets (works with plain podman run)

[Qwarctick]

Describe the bug

When trying to use secrets with podman-compose, I get an error even though the same thing works fine with podman run.

To Reproduce

test-alpine.yml

services:
  alpine_secret:
    image: alpine:latest
    secrets:
      - source: ssh-private-key
        target: /tmp/private_key 
        mode: 700
        uid: 600
        gid: 600
    entrypoint: ["sh", "-c", "ls -alh /tmp && cat /tmpt/secret_key"]

secrets:
  ssh-private-key:
    external: true

podman compose -f test-alpine.yml up

Error output

>>>> Executing external compose provider "/home/vagrant/.local/bin/podman-compose". Please see podman-compose(1) for how to disable this message. <<<<

Error: no container with name or ID "vagrant_alpine_secret_1" found: no such container
Error: no container with ID or name "vagrant_alpine_secret_1" found: no such container
Error: not all containers could be removed from pod ...
...
ValueError: ERROR: Custom name/target reference "/tmp/secret_key" for mounted external secret "secret_key" is not supported
Error: executing /home/vagrant/.local/bin/podman-compose -f test-alpine.yml up: exit status 1

What works with plain podman

This works fine when using podman run directly:

podman run -it --rm \
  --secret=ssh-private-key,uid=600,gid=600,mode=700,type=mount,target=/tmp/private_key \
  alpine:latest sh -c "ls -alh /tmp && cat /tmp/private_key"

Output

-rwx------    1 600      600          411 Aug 19 14:38 private_key
-----BEGIN OPENSSH PRIVATE KEY-----
...
-----END OPENSSH PRIVATE KEY-----

Environment:

$ podman-compose version
podman-compose version 1.5.0
podman version 5.4.0

$ podman version
Client:       Podman Engine
Version:      5.4.0
API Version:  5.4.0
Go Version:   go1.23.9 (Red Hat 1.23.9-1.el9_6)
Built:        Tue Jul  8 03:48:42 2025
OS/Arch:      linux/amd64

$ hostnamectl

 Static hostname: sipa
       Icon name: computer-vm
         Chassis: vm 🖴
      Machine ID: b9ca0673f9d446d9bedbf42499ce723e
         Boot ID: 58018b3af1b7480b9938c93a99c26466
  Virtualization: kvm
Operating System: AlmaLinux 9.6 (Sage Margay)
     CPE OS Name: cpe:/o:almalinux:almalinux:9::baseos
          Kernel: Linux 5.14.0-570.33.2.el9_6.x86_64
    Architecture: x86-64
 Hardware Vendor: QEMU
  Hardware Model: Ubuntu 24.04 PC _i440FX + PIIX, 1996_
Firmware Version: 1.16.3-debian-1.16.3-2

Additional information

I suppose the problem comes from https://github.com/containers/podman-compose/blob/main/podman_compose.py#L703. I can prepare a MR to fix the condition.