The Arch Linux packaging for redo-sh sucks:

I have implemented the build system redo as designed by DJB in Bourne Shell. To understand how redo can be simpler, more flexible, more powerful and more reliable than make, read Introduction to redo and/or redo: a top-down software build system. The current version of redo is $(redo-ifchange ./redo; ./redo --version 2>&1 | head -n1).

redo
the main program
redo-always
marks the current target as always needing to be rebuilt
redo-dot
prints redo dependency graph in DOT format (example output, example rendering)
redo-ifchange
adds dependencies for the current target (if a dependency changes, the target will be rebuilt)
redo-ifcreate
adds non-existence dependencies for the current target (if a non-existence dependency is created, the target will be rebuilt)
redo-ood
prints a list of all target files that are out of date
redo-targets
prints a list of all target files that exist (a target is a file redo can build)
redo-sources
prints a list of all source files that exist (a source is a dependency that is not a target)
redo-stamp
detects if the current target has changed (see apenwarr's documentation)
redo-whichdo
prints search paths for dofiles to build a redo target
redo-gcc
automatically tracks dependencies and non-existence dependencies when compiling using gcc.

Installation

To install redo, copy the redo executables and man pages (detached PGP signature) to a directory in your \$PATH. For example, if /usr/local/bin exists, is listed in your \$PATH and can be written to by the current user, the following commands will install redo:

wget http://news.dieweltistgarnichtso.net/bin/archives/redo-sh.tar.gz
tar -moxzf redo-sh.tar.gz -C /usr/local

This website is hosted in Germany and German police is legally allowed to spread malware. I therefore strongly recommend to verify the PGP signature before installation to ensure that the redo release archive has not been tampered with. If you have gpg installed and trust my PGP signing key, the following commands will install redo only if the signature matches:

wget http://news.dieweltistgarnichtso.net/bin/archives/redo-sh.tar.gz http://news.dieweltistgarnichtso.net/bin/archives/redo-sh.tar.gz.sig
gpg --verify redo-sh.tar.gz.sig redo-sh.tar.gz && tar -moxzf redo-sh.tar.gz -C /usr/local

This implementation of redo depends only on GNU Core Utilities or BusyBox.