Alpine Package Keeper (apk) is a package manager originally built for Alpine Linux, but now used by several other distributions as well.
The preferred build system for building apk-tools is Meson:
# meson setup build --prefix=/
# meson compile -C build
# meson install -C build
While there is a legacy Makefile-based system available, it only works for musl-linux targets, and will be dropped in the apk-tools 3.0 release.
Online documentation is available in the doc/ directory in the form of man pages.
The apk(8) man page provides a basic overview of the package management system.