mmdebstrap uses group name instead of user name for /etc/subgid lookup

[Pengcheng Xu]

For the unshare mode of operation, mmdebstrap checks /etc/subgid for the user's primary group name to see if rootless operation is correctly configured. This is however not the correct behaviour as /etc/subgid contains the user name and the allowed GID map. This prevents proper configuration when the user's primary group name does not coincide with the user name.

This issue has been fixed by upstream already in commit https://gitlab.mister-muffin.de/josch/mmdebstrap/commit/374ae3dc99e5d8a5a176939c3846e790e890a0e7, but is not yet backported into jammy.

Thanks a lot!

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: mmdebstrap 0.8.4-1ubuntu0.1
ProcVersionSignature: Ubuntu 5.15.0-122.132-generic 5.15.163
Uname: Linux 5.15.0-122-generic x86_64
NonfreeKernelModules: zfs zunicode zavl icp zcommon znvpair
ApportVersion: 2.20.11-0ubuntu82.6
Architecture: amd64
CasperMD5CheckResult: unknown
Date: Sun Oct 20 09:08:14 2024
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=C.UTF-8
 SHELL=/bin/zsh
RebootRequiredPkgs: Error: path contained symlinks.
SourcePackage: mmdebstrap
UpgradeStatus: No upgrade log present (probably fresh install)