ms uses wrong location for ini files (data directories) in su environment

[jan.hradek]

Description:
MidnightCommander? uses the ini location of the logged-in user, instead of the user I "su"-ed into. "su -" (login shell) works as expected.
(happened on archlinux, bug report: ​https://bugs.archlinux.org/task/28322)

• version(s): (i686) 4.8.1 - i've also tried current git with the same results
• config and/or log files etc.: /etc/mc/ configuration files are untouched (from arch repositories, i will provide them if you ask for them)

Steps to reproduce:

• login as a regular user (let's use "foo" as our regular user)
• run mc and change configuration, I recommend to change something in the directory hotlist (Ctrl + \)
• save your configuration
• quit mc (F10)
• su (to root), not the login shell "su -" which works ok.
• now run mc in the su enviroment
• (now mc reads the configuration of the regular user "foo")
• NOTE: you can run 'mc -F' to actually see what data directories mc uses
• go to the directory hotlist (Ctrl + \), you should see the hotlist of the logged-in user "foo", not the one you "su"d into
• also if you try to save the configuration, mc clearly states where the config is written - to the user logged in "foo"
• this is reproducible the other way too: login as root and su to some regular user

NOTES:

• this bug has somewhat ugly side effect: if you save the configuration in the su environment then the ownership and the contents of "foo"'s ini files change (obviously)
• mc's internal cd command (just type in "cd" and enter) changes correctly to the home of the su'd user.

Version, config and build information:
# LC_MESSAGES=C mc -V
GNU Midnight Commander 4.8.1
Built with GLib 2.30.2
Using the S-Lang library with terminfo database
With builtin Editor
With subshell support as default
With support for background operations
With mouse support on xterm and Linux console
With support for X11 events
With internationalization support
With multiple codepages support
Virtual File Systems: cpiofs, tarfs, sfs, extfs, ftpfs, fish, smbfs
Data types: char: 8; int: 32; long: 32; void *: 32; size_t: 32; off_t: 64;

# LC_MESSAGES=C mc -F
[System data]

Config directory: /etc/mc/
Data directory: /usr/share/mc/
VFS plugins and scripts: /usr/lib/mc/

extfs.d: /usr/lib/mc/extfs.d/
fish: /usr/lib/mc/fish/

[User data]

Config directory: /home/jh/.config/mc/
Data directory: /home/jh/.local/share/mc/

skins: /home/jh/.local/share/mc/skins/
extfs.d: /home/jh/.local/share/mc/extfs.d/
fish: /home/jh/.local/share/mc/fish/

Cache directory: /home/jh/.cache/mc/

# mc --configure-options

'--prefix=/usr' '--sysconfdir=/etc' '--mandir=/usr/share/man' '--enable-background' '--enable-charset' '--enable-largefile' '--with-edit' '--with-gpm-mouse' '--with-mmap' '--enable-vfs-smb' '--with-screen=slang' '--with-subshell' '--with-vfs' '--with-x' '--without-debug' '--without-gnome' '--without-included-gettext' '--libexecdir=/usr/lib' 'CFLAGS=-march=i686 -mtune=generic -O2 -pipe -fstack-protector --param=ssp-buffer-size=4 -D_FORTIFY_SOURCE=2' 'LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,--hash-style=gnu'