docs: Address review comments by @Zimmi48

README.md

@@ -34,12 +34,10 @@ configuration and boilerplate files in the
 [AAC Tactics](https://github.com/coq-community/aac-tactics)
 project are generated as follows:
 ```shell
-mustache meta.yml ../templates/default.nix.mustache > default.nix
 mustache meta.yml ../templates/README.md.mustache > README.md
-mustache meta.yml ../templates/.travis.yml.mustache > .travis.yml
 mustache meta.yml ../templates/coq.opam.mustache > coq-aac-tactics.opam
-mkdir -p .github/workflows
-mustache meta.yml ../templates/coq-action.yml.mustache > .github/workflows/coq-action.yml
+mustache meta.yml ../templates/default.nix.mustache > default.nix
+mustache meta.yml ../templates/.travis.yml.mustache > .travis.yml
 ```
 Other projects using the templates in a similar way include
 [Chapar](https://github.com/coq-community/chapar) and
@@ -54,6 +52,14 @@ cd -
 ../templates/generate.sh
 git add <the_generated_files>
 ```
+Regarding continuous integration, the `generate.sh` script will create:
+* a [Travis CI](https://docs.travis-ci.com/) configuration
+    [(based on opam + Nix)](./.travis.yml.mustache),
+* or a [GitHub Action](https://help.github.com/en/actions) workflow
+    [(based on opam)](./coq-action.yml.mustache),
+
+depending on whether `meta.yml` contains `travis: true` or `action: true`.
+
 Keeping generated files under version control is not ideal, but `README.md` has to exist,
 and generally this is a common practice when using build systems such as Autotools.
 To get a `mustache` tool in, e.g., NixOS, you can run `nix-env -i mustache-go`.

generate.sh

@@ -2,9 +2,6 @@
 
 srcdir=$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null && pwd )
 
-# ask1() { local yn; echo -n "$* [Y/n] "; read -r -n 1 yn; [[ "$yn" =~ [Yy] ]] && echo && return 0; [ -z "$yn" ] && return 0; echo; return 1; }
-# if ask1 "Question?"; then ...; else ...; fi
-
 get_yaml() {
     # Arg 1: the meta.yml path
     # STDIN: the mustache code
@@ -45,7 +42,7 @@ for f in "$srcdir"/{,.}*.mustache; do
                 continue
             fi
             ;;
-        .travis.yml | default.nix)
+        .travis.yml)
             mustache='{{ travis }}'
             bool=$(get_yaml meta.yml <<<"$mustache")
             if [ -n "$bool" ] && [ "$bool" != false ]; then
@@ -54,6 +51,15 @@ for f in "$srcdir"/{,.}*.mustache; do
                 continue
             fi
             ;;
+        default.nix)
+            mustache='{{ tested_coq_nix_versions }}'
+            bool=$(get_yaml meta.yml <<<"$mustache")
+            if [ -n "$bool" ] && [ "$bool" != false ]; then
+                : noop
+            else
+                continue
+            fi
+            ;;
     esac
     echo "Generating $target..."
     mustache meta.yml "$f" > "$target"