CI commentary

.gitlab-ci.yml

+## Notes (mainly for @rae):
+##
+##  We need both ott and latex in order to build. I don't know how to make
+##  a docker image, so I needed existing docker images. Ocaml helpfully
+##  supplies images with a working opam. And `opam install ott` works.
+##  A quick search on hub.docker.com found aergus/latex, which seems well-used
+##  and well-liked. So that's what we use here.
+##
+##  The "tags" entries below are necessary. Otherwise, we sometimes get
+##  a Windows machine and chaos ensues.
+##
+##  "stages" forces the build-tex to happen before build-pdf. Otherwise, they
+##  would go in parallel, which is all wrong.
+##
+##  "artifacts" labels bits that we want to keep. We need the .tex artifacts
+##  from build-tex just to communicate to build-pdf. I thought of having
+##  a short expiry, but it might be nice one day to be able to examine the
+##  intermediate output.
+##
+##  The build-pdf script uses `touch` to make sure that the haskell.tex
+##  and ott.tex files don't attempt to be rebuilt. I'm sure there's a better
+##  way, but this ensures that this script uses the same build procedure as
+##  I do when I `make`.
+##
+##  "dependencies" are to explicitly declare which artifacts are necessary.
+##  I believe it's optional. It does *not* control ordering; "stages" does that.
+##  I think all it does is avoid getting the non-dependent artifacts. Anyway,
+##  this works.
+
 stages:
   - tex
   - pdf