Update interpreter test output

This also makes a couple minor changes re: running the script:

- removes the “belt and suspenders” `echo`ing that resulted in things being printed in triplicate
- added `gettext` to the Nix environment,  so `envsubst` is available
- changed the #!, to not get stuck with Bash 3.2 on macOS.

nix/haskell-nix-flake.nix

@@ -32,6 +32,7 @@
         (args.nativeBuildInputs or [])
         ++ [
           pkgs.cachix
+          pkgs.gettext # for envsubst, used by unison-src/builtin-tests/interpreter-tests.sh
           pkgs.hpack
           pkgs.pkg-config
           pkgs.stack-wrapped

unison-src/builtin-tests/interpreter-tests.output.md

@@ -4,13 +4,21 @@ If you want to add or update tests, you can create a branch of that project, and
 
 Before merging the PR on Github, we'll merge your branch on Share and restore `runtime_tests_version` to /main or maybe a release.
 
+``` ucm :hide:error
+scratch/main> this is a hack to trigger an error, in order to swallow any error on the next line.
+scratch/main> we delete the project to avoid any merge conflicts or complaints from ucm.
+scratch/main> delete.project runtime-tests
+```
+
+``` ucm :hide
+scratch/main> clone @unison/runtime-tests/releases/0.0.1 runtime-tests/selected
+```
+
 ``` ucm
 runtime-tests/selected> run tests
 
   ()
-
 runtime-tests/selected> run tests.interpreter.only
 
   ()
-
 ```

unison-src/builtin-tests/interpreter-tests.sh

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -ex
 
 if [ -z "$1" ]; then
@@ -8,13 +8,11 @@ else
 fi
 
 runtime_tests_version="@unison/runtime-tests/releases/0.0.1"
-echo $runtime_tests_version
 
 codebase=${XDG_CACHE_HOME:-"$HOME/.cache"}/unisonlanguage/runtime-tests.unison
 
 runtime_tests_version="$runtime_tests_version" \
     envsubst '$runtime_tests_version' \
     < unison-src/builtin-tests/interpreter-tests.tpl.md \
     > unison-src/builtin-tests/interpreter-tests.md
-echo "$ucm" transcript.fork -C $codebase -S $codebase unison-src/builtin-tests/interpreter-tests.md
 time "$ucm" transcript.fork -C $codebase -S $codebase unison-src/builtin-tests/interpreter-tests.md