GNU shtool is a compilation of small but very stable and portable shell scripts into a single shell tool.
All ingredients were in successful use over many years in various free software projects. The compiled shtool program is intended to be used inside the source tree of other free software packages.
There it can overtake various (usually non-portable) tasks related to the building and installation of such a package. GNU shtool especially can replace the old mkdir.sh, install.sh and related scripts.