From 1a51ec2e964cf07e608af262f162034dc7594233 Mon Sep 17 00:00:00 2001
From: "Vojtech Vitek (V-Teq)" <vojtech.vitek@pressly.com>
Date: Mon, 20 Jun 2016 15:24:25 -0400
Subject: [PATCH] Add up-by-one goose command

---
 goose.go   |  4 ++++
 migrate.go | 31 +++++++++++++++++++++++++++++++
 up.go      | 14 ++++++++++++++
 3 files changed, 49 insertions(+)

diff --git a/goose.go b/goose.go
index 21039bb..1f2a75b 100644
--- a/goose.go
+++ b/goose.go
@@ -11,6 +11,10 @@ func Run(command string, db *sql.DB, dir string) error {
 		if err := Up(db, dir); err != nil {
 			return err
 		}
+	case "up-by-one":
+		if err := UpByOne(db, dir); err != nil {
+			return err
+		}
 	case "down":
 		if err := Down(db, dir); err != nil {
 			return err
diff --git a/migrate.go b/migrate.go
index c1f8fa4..c0bb42a 100644
--- a/migrate.go
+++ b/migrate.go
@@ -17,6 +17,7 @@ import (
 
 var (
 	ErrNoPreviousVersion = errors.New("no previous version found")
+	ErrNoNextVersion     = errors.New("no next version found")
 	goMigrations         []*Migration
 )
 
@@ -56,6 +57,11 @@ func RunMigrations(db *sql.DB, dir string, target int64) (err error) {
 		return err
 	}
 
+	if current == target {
+		fmt.Printf("goose: no migrations to run. current version: %d. target version: %d\n", current, target)
+		return nil
+	}
+
 	migrations, err := CollectMigrations(dir, current, target)
 	if err != nil {
 		return err
@@ -322,6 +328,31 @@ func GetPreviousDBVersion(dirpath string, version int64) (previous int64, err er
 	return
 }
 
+func GetNextDBVersion(dirpath string, version int64) (next int64, err error) {
+
+	next = 9223372036854775807 // max(int64)
+
+	filepath.Walk(dirpath, func(name string, info os.FileInfo, walkerr error) error {
+
+		if !info.IsDir() {
+			if v, e := NumericComponent(name); e == nil {
+				if v < next && v > version {
+					next = v
+				}
+			}
+		}
+
+		return nil
+	})
+
+	if next == 9223372036854775807 {
+		next = version
+		err = ErrNoNextVersion
+	}
+
+	return
+}
+
 // helper to identify the most recent possible version
 // within a folder of migration scripts
 func GetMostRecentDBVersion(dirpath string) (version int64, err error) {
diff --git a/up.go b/up.go
index 79c9807..6788164 100644
--- a/up.go
+++ b/up.go
@@ -15,3 +15,17 @@ func Up(db *sql.DB, dir string) error {
 	}
 	return nil
 }
+
+func UpByOne(db *sql.DB, dir string) error {
+	current, err := GetDBVersion(db)
+	if err != nil {
+		return err
+	}
+
+	next, _ := GetNextDBVersion(dir, current)
+	if err = RunMigrations(db, dir, next); err != nil {
+		return err
+	}
+
+	return nil
+}