[fmt] [dune] Add ocamlformat configuration.

For now we don't enable it in any source file, neither on dune files.

`lint-repository` has been updated so it will check `dune build @fmt`
returns 0.

1 files changed, 5 insertions, 0 deletions

diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index e26103cedd..1a12360c13 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -497,6 +497,11 @@ We have a linter that checks a few different things:
   your branch with `git rebase --whitespace=fix`.
 - **All files should end with a single newline**.  See the section
   [Style guide](#style-guide) for additional style recommendations.
+- **Code is properly formatted**: for some parts of the codebase,
+  formatting will be enforced using the
+  [`ocamlformat`](https://github.com/ocaml-ppx/ocamlformat) tool. You
+  can integrate the formatter in your editor of choice (see docs) or
+  use `dune build @fmt --auto-promote` to fix this kind of errors.
 
 You may run the linter yourself with `dev/lint-repository.sh`.