preinst is in cdecl 2.5-13build1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 | #!/bin/sh -e
if [ "$1" = upgrade ]; then
    if [ -n "`dpkg-divert --list | grep /usr/man/man1/cdecl.1.cutils`" ]; then
        if [ -f /usr/man/man1/cdecl.1.gz ]; then
    	    rm /usr/man/man1/cdecl.1.gz
	fi
        dpkg-divert --package cdecl --remove --rename \
	    --divert /usr/man/man1/cdecl.1.cutils.gz /usr/man/man1/cdecl.1.gz
        dpkg-divert --package cdecl --add --rename \
   	    --divert /usr/share/man/man1/cdecl.cutils.1.gz /usr/share/man/man1/cdecl.1.gz
    fi
    if [ -n "`dpkg-divert --list | grep /usr/share/man/man1/cdecl.1.cutils`" ]; then
        if [ -f /usr/share/man/man1/cdecl.1.gz ]; then
    	    rm /usr/share/man/man1/cdecl.1.gz
	fi
        dpkg-divert --package cdecl --remove --rename \
	    --divert /usr/share/man/man1/cdecl.1.cutils.gz /usr/share/man/man1/cdecl.1.gz
        dpkg-divert --package cdecl --add --rename \
   	    --divert /usr/share/man/man1/cdecl.cutils.1.gz /usr/share/man/man1/cdecl.1.gz
    fi
fi
if [ "$1" = install ]; then
    dpkg-divert --package cdecl --add --rename \
	--divert /usr/bin/cdecl.cutils /usr/bin/cdecl
    dpkg-divert --package cdecl --add --rename \
	--divert /usr/share/man/man1/cdecl.cutils.1.gz /usr/share/man/man1/cdecl.1.gz
fi
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