options: request absent flag, warn; --strict fails

unrecognised options are named on stderr before any work is done, and
--strict makes such fatal (exit 1). (prior to this commit a mistyped
or retired flag was ignored without acknowledgement). This applies to
options only, an argument that is not a source, such as a README beside
pods being processed, is still passed over quietly.

(assisted by Claude-Code)

1 files changed, 13 insertions, 0 deletions

diff --git a/src/sisudoc/spine.d b/src/sisudoc/spine.d
index db6c8ac..e1e5d62 100644
--- a/src/sisudoc/spine.d
+++ b/src/sisudoc/spine.d
@@ -395,6 +395,19 @@ string program_name = "spine";
   if (opts["po4a-cfg"]) {
     _run_banner = false;
   }
+  /+ ↓ an option getopt did not recognise +/
+  {
+    string[] _unknown_options
+      = args[1..$].filter!(a => a.length > 1 && a[0] == '-').array;
+    foreach (_o; _unknown_options) {
+      stderr.writeln("WARNING: option not recognised, ignored: ", _o);
+    }
+    if (_unknown_options.length > 0 && opts["strict"]) {
+      stderr.writeln("~ run FAILED ~ --strict: option not recognised");
+      import core.stdc.stdlib : exit;
+      exit(1);
+    }
+  }
   if (helpInfo.helpWanted) {
     /+ ↓ the undocumented alias is registered so that it still works, and is
          not listed, so that --ocda-db is the one flag the help offers