If there is no TTY, also skip verbose sudo messages

scripts/install-darwin-multi-user.sh

@@ -49,6 +49,14 @@ else
     readonly IS_HEADLESS='yes'
 fi
 
+headless() {
+    if [ "$IS_HEADLESS" = "yes" ]; then
+        return 0
+    else
+        return 1
+    fi
+}
+
 contactme() {
     echo "We'd love to help if you need it."
     echo ""
@@ -179,7 +187,7 @@ failure() {
 ui_confirm() {
     _textout "$GREEN$GREEN_UL" "$1"
 
-    if [ "$IS_HEADLESS" = "yes" ]; then
+    if headless; then
         echo "No TTY, assuming you would say yes :)"
         return 0
     fi
@@ -221,9 +229,10 @@ __sudo() {
 _sudo() {
     local expl="$1"
     shift
-    if __sudo "$expl" "$*"; then
-        sudo "$@"
+    if ! headless; then
+        __sudo "$expl" "$*"
     fi
+    sudo "$@"
 }
 
 
@@ -620,6 +629,27 @@ EOF
 chat_about_sudo() {
     header "let's talk about sudo"
 
+    if headless; then
+        cat <<EOF
+This script is going to call sudo a lot. Normally, it would show you
+exactly what commands it is running and why. However, the script is
+run in  a headless fashion, like this:
+
+  $ curl https://nixos.org/nix/install | sh
+
+or maybe in a CI pipeline. Because of that, we're going to skip the
+verbose output in the interest of brevity.
+
+If you would like to
+see the output, try like this:
+
+  $ curl -o install-nix https://nixos.org/nix/install
+  $ sh ./install-nix
+
+EOF
+        return 0
+    fi
+
     cat <<EOF
 This script is going to call sudo a lot. Every time we do, it'll
 output exactly what it'll do, and why.