support --env-file CLI option (#274)

README.md

@@ -138,6 +138,7 @@ The following options are available with all commands. You must use command line
 
 - `--url, -u "protocol://host:port/dbname"` - specify the database url directly. _(env: `DATABASE_URL`)_
 - `--env, -e "DATABASE_URL"` - specify an environment variable to read the database connection URL from.
+- `--env-file "./env"` - specify an alternate environment variables file to load.
 - `--migrations-dir, -d "./db/migrations"` - where to keep the migration files. _(env: `DBMATE_MIGRATIONS_DIR`)_
 - `--migrations-table "schema_migrations"` - database table to record migrations in. _(env: `DBMATE_MIGRATIONS_TABLE`)_
 - `--schema-file, -s "./db/schema.sql"` - a path to keep the schema.sql file. _(env: `DBMATE_SCHEMA_FILE`)_

main.go

@@ -17,8 +17,6 @@ import (
 )
 
 func main() {
-	loadDotEnv()
-
 	app := NewApp()
 	err := app.Run(os.Args)
 
@@ -37,6 +35,16 @@ func NewApp() *cli.App {
 	app.Version = dbmate.Version
 
 	defaultDB := dbmate.New(nil)
+
+	app.Before = func(c *cli.Context) error {
+		if err := loadDotEnv(c.String("env-file")); err != nil {
+			log.Fatalf(err.Error())
+			return err
+		}
+
+		return nil
+	}
+
 	app.Flags = []cli.Flag{
 		&cli.StringFlag{
 			Name:    "url",
@@ -49,6 +57,11 @@ func NewApp() *cli.App {
 			Value:   "DATABASE_URL",
 			Usage:   "specify an environment variable containing the database URL",
 		},
+		&cli.StringFlag{
+			Name:  "env-file",
+			Value: ".env",
+			Usage: "specify an env file containing DATABASE_URL",
+		},
 		&cli.StringSliceFlag{
 			Name:    "migrations-dir",
 			Aliases: []string{"d"},
@@ -211,15 +224,19 @@ func NewApp() *cli.App {
 	return app
 }
 
-// load environment variables from .env file
-func loadDotEnv() {
-	if _, err := os.Stat(".env"); err != nil {
-		return
+// load environment variables
+func loadDotEnv(filenames ...string) error {
+	for _, filename := range filenames {
+		if _, err := os.Stat(filename); err != nil {
+			return nil
+		}
 	}
 
-	if err := godotenv.Load(); err != nil {
-		log.Fatalf("Error loading .env file: %s", err.Error())
+	if err := godotenv.Load(filenames...); err != nil {
+		return fmt.Errorf("Error loading env file: %s", err.Error())
 	}
+
+	return nil
 }
 
 // action wraps a cli.ActionFunc with dbmate initialization logic