Remove migrate.FS interface and Migrator.Path field

Turns out these are not needed when using `fs.Sub`, `fs.ReadFile`, and `fs.ReadDir` functions.

README.md

@@ -15,6 +15,7 @@ import (
 	"context"
 	"database/sql"
 	"embed"
+	"io/fs"
 
 	_ "github.com/jackc/pgx/v4/stdlib"
 	"github.com/maragudk/migrate"
@@ -26,15 +27,18 @@ import (
 // migrations/2.up.sql
 // migrations/2.down.sql
 //go:embed migrations
-var migrations embed.FS
+var dir embed.FS
 
 func main() {
 	db, err := sql.Open("pgx", "postgresql://postgres:123@localhost:5432/postgres?sslmode=disable")
 	if err != nil {
 		panic(err)
 	}
+	migrations, err := fs.Sub(dir, "migrations")
+	if err != nil {
+		panic(err)
+	}
 	m := migrate.New(db, migrations)
-	m.Path = "migrations"
 	if err := m.MigrateUp(context.Background()); err != nil {
 		panic(err)
 	}

migrate.go

@@ -7,7 +7,6 @@ import (
 	"errors"
 	"fmt"
 	"io/fs"
-	"path"
 	"regexp"
 )
 
@@ -16,23 +15,16 @@ var (
 	downMatcher = regexp.MustCompile(`^([\w]+).down.sql`)
 )
 
-type FS interface {
-	fs.ReadDirFS
-	fs.ReadFileFS
-}
-
 type Migrator struct {
-	DB   *sql.DB
-	FS   FS
-	Path string
+	DB *sql.DB
+	FS fs.FS
 }
 
 // New Migrator with default options.
-func New(db *sql.DB, fs FS) *Migrator {
+func New(db *sql.DB, fs fs.FS) *Migrator {
 	return &Migrator{
-		DB:   db,
-		FS:   fs,
-		Path: ".",
+		DB: db,
+		FS: fs,
 	}
 }
 
@@ -104,7 +96,7 @@ func (m *Migrator) MigrateDown(ctx context.Context) error {
 
 // apply a file identified by name and update to version.
 func (m *Migrator) apply(ctx context.Context, name, version string) error {
-	content, err := m.FS.ReadFile(path.Join(m.Path, name))
+	content, err := fs.ReadFile(m.FS, name)
 	if err != nil {
 		return err
 	}
@@ -122,7 +114,7 @@ func (m *Migrator) apply(ctx context.Context, name, version string) error {
 // getFilenames alphabetically where the name matches the given matcher.
 func (m *Migrator) getFilenames(matcher *regexp.Regexp) ([]string, error) {
 	var names []string
-	entries, err := m.FS.ReadDir(m.Path)
+	entries, err := fs.ReadDir(m.FS, ".")
 	if err != nil {
 		return names, err
 	}

migrate_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"database/sql"
 	"embed"
+	"io/fs"
 	"testing"
 	"testing/fstest"
 
@@ -23,9 +24,8 @@ func TestMigrator_MigrateUp(t *testing.T) {
 		is := is.New(t)
 
 		m := migrate.Migrator{
-			DB:   db,
-			FS:   fstest.MapFS{},
-			Path: ".",
+			DB: db,
+			FS: fstest.MapFS{},
 		}
 
 		err := m.MigrateUp(context.Background())
@@ -43,9 +43,8 @@ func TestMigrator_MigrateUp(t *testing.T) {
 		is := is.New(t)
 
 		m := migrate.Migrator{
-			DB:   db,
-			FS:   testdata,
-			Path: "testdata/two",
+			DB: db,
+			FS: mustSub(t, testdata, "testdata/two"),
 		}
 
 		err := m.MigrateUp(context.Background())
@@ -63,9 +62,8 @@ func TestMigrator_MigrateUp(t *testing.T) {
 		is := is.New(t)
 
 		m := migrate.Migrator{
-			DB:   db,
-			FS:   testdata,
-			Path: "testdata/two",
+			DB: db,
+			FS: mustSub(t, testdata, "testdata/two"),
 		}
 
 		err := m.MigrateUp(context.Background())
@@ -81,9 +79,8 @@ func TestMigrator_MigrateUp(t *testing.T) {
 		is := is.New(t)
 
 		m := migrate.Migrator{
-			DB:   db,
-			FS:   testdata,
-			Path: "testdata/bad",
+			DB: db,
+			FS: mustSub(t, testdata, "testdata/bad"),
 		}
 
 		err := m.MigrateUp(context.Background())
@@ -104,9 +101,8 @@ func TestMigrator_MigrateDown(t *testing.T) {
 		is := is.New(t)
 
 		m := migrate.Migrator{
-			DB:   db,
-			FS:   testdata,
-			Path: "testdata/two",
+			DB: db,
+			FS: mustSub(t, testdata, "testdata/two"),
 		}
 
 		err := m.MigrateUp(context.Background())
@@ -132,9 +128,8 @@ func TestMigrator_MigrateDown(t *testing.T) {
 		is := is.New(t)
 
 		m := migrate.Migrator{
-			DB:   db,
-			FS:   testdata,
-			Path: "testdata/two",
+			DB: db,
+			FS: mustSub(t, testdata, "testdata/two"),
 		}
 
 		err := m.MigrateDown(context.Background())
@@ -150,8 +145,11 @@ func Example() {
 	if err != nil {
 		panic(err)
 	}
-	m := migrate.New(db, exampleFS)
-	m.Path = "testdata/example"
+	migrations, err := fs.Sub(exampleFS, "testdata/example")
+	if err != nil {
+		panic(err)
+	}
+	m := migrate.New(db, migrations)
 	if err := m.MigrateUp(context.Background()); err != nil {
 		panic(err)
 	}
@@ -175,3 +173,13 @@ func createDatabase(t *testing.T) (*sql.DB, func()) {
 		}
 	}
 }
+
+func mustSub(t *testing.T, fsys fs.FS, path string) fs.FS {
+	t.Helper()
+	fsys, err := fs.Sub(fsys, path)
+	if err != nil {
+		t.Log(err)
+		t.FailNow()
+	}
+	return fsys
+}