Fixup --slurpfile/argile docs

docs/content/3.manual/manual.yml

@@ -219,8 +219,11 @@ sections:
 
       * `--argfile variable-name filename`:
 
-        Like `--slurpfile`, but uses just the first value in the given
-        file.
+        Do not use.  Use `--slurpfile` instead.
+
+        (This option is like `--slurpfile`, but when the file has just
+        one text, then that is used, else an array of texts is used as
+        in `--slurfile`.)
 
   - title: Basic filters
     entries:

main.c

@@ -49,7 +49,7 @@ static void usage(int code) {
   BAIL(fprintf(f, "\t -R\t\tread raw strings, not JSON texts;\n"));
   BAIL(fprintf(f, "\t --arg a v\tset variable $a to value <v>;\n"));
   BAIL(fprintf(f, "\t --argjson a v\tset variable $a to JSON value <v>;\n"));
-  BAIL(fprintf(f, "\t --argfile a f\tset variable $a to JSON texts read from <f>;\n"));
+  BAIL(fprintf(f, "\t --slurpfile a f\tset variable $a to an array of JSON texts read from <f>;\n"));
   BAIL(fprintf(f, "\tSee the manpage for more options.\n"));
   exit(code);
 }