[dune] Shim for starting `coqtop/coqide` with minimal config.

As requested by Gaëtan Gilbert, we add shims

- `dev/shim/coqtop-prelude`
- `dev/shim/coqide-prelude`

that will build and start `coqtop` and `coqide` with just the prelude
loaded properly.

`dune exec dev/shim/coqtop-prelude` will build and execute this shim,
equivalent to doing `make states && bin/coqtop` under the old model.

This PR is just a bit of "a hack" until proper support for Coq
libraries arrives to Dune, however there is nothing wrong with it.

In particular, we must bootstrap `coq.plugins.ltac` as Dune needs to
compute the full installation path to allow `%{bin:foo}` in deps,
[this is a kind of shortcoming of the current implementation, and the
error message is just terrible]

We cannot depend on installed `.vo` files without doing a gross hack
[including them inside an ml lib] so for now we just depend on their
non-installed forms. Using `%{bin}` is good enough for the shims who
would like to locate binaries using `PATH`.

The long term plan (for now) is to have a command similar to `dune
utop $dir`, `dune coqtop $dir`, which would spawn a proper Coq shell
with the corresponding libraries on the path.

This will work for `dir=stdlib/Init/` for example, or for any other
combination.

1 files changed, 18 insertions, 0 deletions

diff --git a/dev/doc/build-system.dune.md b/dev/doc/build-system.dune.md
index da91c85856..a31ab1c511 100644
--- a/dev/doc/build-system.dune.md
+++ b/dev/doc/build-system.dune.md
@@ -44,6 +44,24 @@ Dune will read the file `~/.config/dune/config`; see `man
 dune-config`. Among others, you can set in this file the custom number
 of build threads `(jobs N)` and display options `(display _mode_)`.
 
+## Running binaries [coqtop / coqide]
+
+There are two special targets `states` and `quickide` that will
+generate "shims" for running `coqtop` and `coqide` in a fast build. In
+order to use them, do:
+
+```
+$ make -f Makefile.dune voboot                # Only once per session
+$ dune exec dev/shim/coqtop-prelude
+```
+
+or `quickide` / `dev/shim/coqide-prelude` for CoqIDE. These targets
+enjoy quick incremental compilation thanks to `-opaque` so they tend
+to be very fast while developing.
+
+Note that for a fast developer build of ML files, the `check` target
+will be faster.
+
 ## Targets
 
 The default dune target is `dune build` (or `dune build @install`),