toolbin/merge_config takes a list of basenames and merges them by
applying them from left to right. If the first basename may refer to a
file or a directory; the resulting merge is of the same type.

Usage:
toolbin/merge_config --merge --dst location [--verbose] base base2 ...

For each basename X up to one of three possible files may exist:
$X - copy $X as result of the merge (overwritting any existing $X)
$X.patch - patch an existing $X
$X.delete - delete an existing $X

toolbin/extract_variants decomposes a string like foo/bar-baz/boing-bu
along the dashes into:
foo/bar-baz-boing-bu
foo/bar-baz-boing
foo/bar-baz
foo/bar

It is used to generate all possible sources merge_config should consider.