relative filename completion

[Stefan `Sec` Zehl <sec@42.org>]

I'm trying to get 'relative filename completion' to work - i.e. a
filename completion which doesnt work relative to '.', but relative to
some other Directory. ("compctl -g '~/Mail/*(:t)' mutt" is not able to
complete in subdirs). So far i tried various things, and the closest i
could come up with was:
compctl -g '~/Mail/**/*(:s_/home/sec/Mail/__)' mutt

I was told to look at "Functions/cdmatch" but that didn't work very
well, too:

compctl -K gkomp g

gkomp () {
        setopt localoptions
        local narg pref cdp
        read -nc narg
        read -Ac pref
        cdp=(~/Mail) 
        reply=(${^cdp}/${pref[$narg]%$2}*$2(-DN^M:t)) 
}

It offers me all files/directories in ~/Mail, but I'm not able to complete
files in one of these directories.

If anybody could help me here?

CU,
    Sec
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