plumbing directly very often, but it can be good to know what the
plumbing does for when the porcelain isn't flushing.
+Back when this document was originally written, many porcelain
+commands were shell scripts. For simplicity, it still uses them as
+examples to illustrate how plumbing is fit together to form the
+porcelain commands. The source tree includes some of these scripts in
+contrib/examples/ for reference. Although these are not implemented as
+shell scripts anymore, the description of what the plumbing layer
+commands do is still valid.
+
[NOTE]
Deeper technical details are often marked as Notes, which you can
skip on your first reading.