Aports tree
The aports tree contains a directory with the corresponding APKBUILD file for every package/program. APKBUILD is a file containing "recipes" on how something should be built/compiled. These files are used when building Alpine from source.
When Alpine Linux is compiled, you will no longer see (or have use of) the APKBUILD. It is not included in the 'iso' or 'tar.gz'. The abuild script reads the APKBUILD and executes the steps needed to create a package.
Directories
There are some directories placed in the aports tree. A short description of every directory can be found in this section.
main
main contains the basic set of packages for Alpine Linux.
community
community contains the additional packages that, for various reasons, are not guaranteed to be supported beyond six months.
testing
All new packages go to testing first. Package will be moved to main if there is positive feedback or for other good reasons. Packages in testing are not included in stable builds, but are only built for edge.
Fetch latest APKBUILD files
While inside your build environment you need to install some needed packages and you need to fetch the APKBUILD's from the server (fetch the aports tree).
Note: You only need to do these 2 steps once! Next time you can skip this part.
apk add alpine-sdk
cd ~
git clone git://git.alpinelinux.org/aports
When the above is done, you might be interested in fetching the latest updates:
cd ~/aports
git pull