sort: Fix bug where --batch-size option shrank SORT_SIZE.

* src/sort.c (specify_nmerge, main): Only adjust SORT_SIZE if it's already set.
* tests/misc/sort-merge: Test bug fix.

src/sort.c

@@ -1105,14 +1105,7 @@ specify_nmerge (int oi, char c, char const *s)
 	      e = LONGINT_OVERFLOW;
 	    }
 	  else
-	    {
-	      /* Need to re-check that we meet the minimum
-		 requirement for memory usage with the new,
-		 potentially larger, nmerge. */
-	      sort_size = MAX (sort_size, MIN_SORT_SIZE);
-
-	      return;
-	    }
+	    return;
 	}
     }
 
@@ -3320,6 +3313,11 @@ main (int argc, char **argv)
       files = −
     }
 
+  /* Need to re-check that we meet the minimum requirement for memory
+     usage with the final value for NMERGE. */
+  if (0 < sort_size)
+    sort_size = MAX (sort_size, MIN_SORT_SIZE);
+
   if (checkonly)
     {
       if (nfiles > 1)

tests/misc/sort-merge

@@ -27,6 +27,8 @@ my $prog = 'sort';
 # three empty files and one that says 'foo'
 my @inputs = (+(map{{IN=> {"empty$_"=> ''}}}1..3), {IN=> {foo=> "foo\n"}});
 
+my $big_input = "aaa\n" x 1024;
+
 # don't need to check for existence, since we're running in a temp dir
 my $badtmp = 'does/not/exist';
 
@@ -66,6 +68,11 @@ my @Tests =
      ['nmerge-no', "-m --batch-size=2 -T$badtmp", @inputs,
         {ERR_SUBST=>"s|: $badtmp/sort.+||"},
         {ERR=>"$prog: cannot create temporary file\n"}, {EXIT=>2}],
+
+     # This used to fail because setting batch-size without also setting
+     # buffer size would cause the buffer size to be set to the minimum.
+     ['batch-size', "--batch-size=16 -T$badtmp", {IN=> {big=> $big_input}},
+	{OUT=>$big_input}],
     );
 
 my $save_temps = $ENV{DEBUG};