source documentation beyond develop.txt #19651

I was wondering, if we should collaborate on documenting certain parts of the code beyond develop.txt.

For example;

Building builds older than v9.0.1930 on newer libs (current date) requires:

git show 9eb1ce5315 -- src/os_unix.c | git apply
git show 4927bc7 -- src/os_unix.c | git apply

Useful if one is bisecting older builds, not to come to same conclusions as others tirelessly.

Other examples could be documenting pieces of various source files that are not easily understood.

I think it would be helpful with a predictable pattern as :help, so if you are working on gui_gtk_x11.c:

You could find help under
:help develop-gui_gtk_x11 (just an idea)
other suggestion
:help src-gui_gtk_x11

... therein could lie explanations ad-hoc basis on functions or mechanisms, notes, warnings so one isn't shooting themselves (and everyone else) in the foot.