-These are original scripted implementations, kept primarily for their
-reference value to any aspiring plumbing users who want to learn how
-pieces can be fit together.
+This directory used to contain scripted implementations of builtins
+that have since been rewritten in C.
+
+They have now been removed, but can be retrieved from an older commit
+that removed them from this directory.
+
+They're interesting for their reference value to any aspiring plumbing
+users who want to learn how pieces can be fit together, but in many
+cases have drifted enough from the actual implementations Git uses to
+be instructive.
+
+Other things that can be useful:
+
+ * Some commands such as git-gc wrap other commands, and what they're
+ doing behind the scenes can be seen by running them under
+ GIT_TRACE=1
+
+ * Doing `git log` on paths matching '*--helper.c' will show
+ incremental effort in the direction of moving existing shell
+ scripts to C.