reftable/writer: improve error when passed an invalid block size

The reftable format only supports block sizes up to 16MB. When the
writer is being passed a value bigger than that it simply calls
abort(3P), which isn't all that helpful due to the lack of a proper
error message.

Improve this by calling `BUG()` instead.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

reftable/writer.c

@@ -128,10 +128,8 @@ reftable_new_writer(ssize_t (*writer_func)(void *, const void *, size_t),
 	if (_opts)
 		opts = *_opts;
 	options_set_defaults(&opts);
-	if (opts.block_size >= (1 << 24)) {
-		/* TODO - error return? */
-		abort();
-	}
+	if (opts.block_size >= (1 << 24))
+		BUG("configured block size exceeds 16MB");
 
 	strbuf_init(&wp->block_writer_data.last_key, 0);
 	strbuf_init(&wp->last_key, 0);