[svckr]

Regarding DAG: tsort (1) sorts input lines by interpreting them as a list of edges. I guess that's what you where referring to when you said "cumbersome" :)

    $ cat > f
    a c
    a d
    b c
    ^D
    $ tsort f
    a
    b
    d
    c

[vog]

The problem is not tsort, it is adding, removing, updating items in such a text file. (not to mention nasty corner cases like filenames containing whitespaces, or the security implications of filenames containing newlines)