nethack --version:dump

Add the 'dump' argument to the existing '--version' command-line
option to display the magic numbers used when validating save and
bones files for compatibility.

Nothing exciting, just a line of 5 hex values.  I was going to also
list the values for however many save and bones files are specified
on the command line but it seems to need more effort than I care to
expend.  And I hadn't made up my mind whether that should be done by
nethack, recover, or some new standalone program.  [Single line of
relatively raw output is so that they could be compared more easily.]

nethack --version:bad-argument was writing a message to stdout and
then starting play--which immediately overwrites stdout.  Have it
quit instead.  Player wasn't trying to start a game and quitting is
what it does with --version:good-argument.

src/allmain.c

@@ -936,7 +936,7 @@ argcheck(int argc, char *argv[], enum earlyarg e_arg)
             break;
     }
     if (idx >= SIZE(earlyopts) || argc < 1)
-        return FALSE;
+        return 0;
 
     for (i = 0; i < argc; ++i) {
         if (argv[i][0] != '-')
@@ -975,13 +975,21 @@ argcheck(int argc, char *argv[], enum earlyarg e_arg)
                        than  next major version */
                 if (match_optname(extended_opt, "paste", 5, FALSE)) {
                     insert_into_pastebuf = TRUE;
-                } else if(match_optname(extended_opt, "copy", 4, FALSE)) {
+                } else if (match_optname(extended_opt, "copy", 4, FALSE)) {
                     insert_into_pastebuf = TRUE;
-                } else {
-                    raw_printf(
-                   "-%sversion can only be extended with -%sversion:copy.\n",
+                } else if (match_optname(extended_opt, "dump", 4, FALSE)) {
+                    /* version number plus enabled features and sanity
+                       values that the program compares against the same
+                       thing recorded in save and bones files to check
+                       whether they're being used compatibly */
+                    dump_version_info();
+                    return 2; /* done */
+                } else if (!match_optname(extended_opt, "show", 4, FALSE)) {
+                    raw_printf("-%sversion can only be extended with"
+                               " -%sversion:copy or :dump or :show.\n",
                                dashdash, dashdash);
-                    return TRUE;
+                    /* exit after we've reported bad command line argument */
+                    return 2;
                 }
             }
             early_version_info(insert_into_pastebuf);
@@ -1016,7 +1024,7 @@ argcheck(int argc, char *argv[], enum earlyarg e_arg)
             break;
         }
     };
-    return FALSE;
+    return 0;
 }
 
 /*

src/version.c

@@ -485,4 +485,26 @@ copyright_banner_line(int indx)
     return "";
 }
 
+/* called by argcheck(allmain.c) from early_options(sys/xxx/xxxmain.c) */
+void
+dump_version_info(void)
+{
+    char buf[BUFSZ];
+    const char *hname = gh.hname ? gh.hname : "nethack";
+
+    if (strlen(hname) > 33)
+        hname = eos(nhStr(hname)) - 33; /* discard const for eos() */
+    runtime_info_init();
+    Snprintf(buf, sizeof buf, "%-12.33s %08lx %08lx %08lx %08lx %08lx",
+             hname,
+             nomakedefs.version_number,
+             (nomakedefs.version_features & ~nomakedefs.ignored_features),
+             nomakedefs.version_sanity1,
+             nomakedefs.version_sanity2,
+             nomakedefs.version_sanity3);
+    raw_print(buf);
+    release_runtime_info();
+    return;
+}
+
 /*version.c*/