p The build is driven by dirdeps.mk using DIRDEPS stored in Makefile.depend files found in each directory.

p The build can be started from anywhere, and behaves the same. The initial instance of make recursively reads DIRDEPS from Makefile.depend computing a graph of tree dependencies from the current origin. See http://www.crufty.net/help/sjg/dirdeps.htm

p As each target is made .Xr make 1 produces a meta file which is used to capture (and compare) the command line, as well as any command output. If .Xr filemon 4 is available the meta file will also capture a record of syscalls used to produce the target.