From 52af0e6a357b39bdf51219affbeefc7d908fdb5e Mon Sep 17 00:00:00 2001
From: "Vojtech Vitek (V-Teq)" <vojtech.vitek@pressly.com>
Date: Mon, 15 Aug 2016 14:11:46 -0400
Subject: [PATCH] Panic on duplicate migration version

---
 migrate.go | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/migrate.go b/migrate.go
index a214a0e..1fabd56 100644
--- a/migrate.go
+++ b/migrate.go
@@ -39,9 +39,14 @@ type Migration struct {
 type migrationSorter []*Migration
 
 // helpers so we can use pkg sort
-func (ms migrationSorter) Len() int           { return len(ms) }
-func (ms migrationSorter) Swap(i, j int)      { ms[i], ms[j] = ms[j], ms[i] }
-func (ms migrationSorter) Less(i, j int) bool { return ms[i].Version < ms[j].Version }
+func (ms migrationSorter) Len() int      { return len(ms) }
+func (ms migrationSorter) Swap(i, j int) { ms[i], ms[j] = ms[j], ms[i] }
+func (ms migrationSorter) Less(i, j int) bool {
+	if ms[i].Version == ms[j].Version {
+		panic(fmt.Sprintf("goose: duplicate version %v detected", ms[i].Version))
+	}
+	return ms[i].Version < ms[j].Version
+}
 
 func AddMigration(up func(*sql.Tx) error, down func(*sql.Tx) error) {
 	_, filename, _, _ := runtime.Caller(1)