* guix/scripts/graph.scm (<node-type>, <graph-backend>, emit-prologue) (emit-epilogue, emit-node, emit-edge, %graphviz-backend, export-graph): Move to... * guix/graph.scm: ... here. New file. * guix/scripts/system.scm, tests/graph.scm: Use it. * Makefile.am (MODULES): Add it.