reset.c: share call to die_if_unmerged_cache()

Use a single condition to guard the call to die_if_unmerged_cache for
both --soft and --keep. This avoids the small distraction of the
precondition check from the logic following it.

Also change an instance of

  if (e)
    err = err || f();

to the almost as short, but clearer

  if (e && !err)
    err = f();

(which is equivalent since we only care whether exit code is 0)

Signed-off-by: Martin von Zweigbergk <martinvonz@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/reset.c

@@ -337,15 +337,13 @@ int cmd_reset(int argc, const char **argv, const char *prefix)
 	/* Soft reset does not touch the index file nor the working tree
 	 * at all, but requires them in a good order.  Other resets reset
 	 * the index file to the tree object we are switching to. */
-	if (reset_type == SOFT)
+	if (reset_type == SOFT || reset_type == KEEP)
 		die_if_unmerged_cache(reset_type);
-	else {
-		int err;
-		if (reset_type == KEEP)
-			die_if_unmerged_cache(reset_type);
-		err = reset_index_file(sha1, reset_type, quiet);
-		if (reset_type == KEEP)
-			err = err || reset_index_file(sha1, MIXED, quiet);
+
+	if (reset_type != SOFT) {
+		int err = reset_index_file(sha1, reset_type, quiet);
+		if (reset_type == KEEP && !err)
+			err = reset_index_file(sha1, MIXED, quiet);
 		if (err)
 			die(_("Could not reset index file to revision '%s'."), rev);
 	}