We should pass around db.Instance instead of leveldb.DB

We're going to need the db.Instance to keep some state, and for that to
work we need the same one passed around everywhere. Hence this moves the
leveldb-specific file opening stuff into the db package and exports the
dbInstance type.

lib/db/set_test.go

@@ -15,8 +15,6 @@ import (
 
 	"github.com/syncthing/syncthing/lib/db"
 	"github.com/syncthing/syncthing/lib/protocol"
-	"github.com/syndtr/goleveldb/leveldb"
-	"github.com/syndtr/goleveldb/leveldb/storage"
 )
 
 var remoteDevice0, remoteDevice1 protocol.DeviceID
@@ -96,11 +94,7 @@ func (l fileList) String() string {
 }
 
 func TestGlobalSet(t *testing.T) {
-
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	m := db.NewFileSet("test", ldb)
 
@@ -303,10 +297,7 @@ func TestGlobalSet(t *testing.T) {
 }
 
 func TestNeedWithInvalid(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	s := db.NewFileSet("test", ldb)
 
@@ -343,10 +334,7 @@ func TestNeedWithInvalid(t *testing.T) {
 }
 
 func TestUpdateToInvalid(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	s := db.NewFileSet("test", ldb)
 
@@ -378,10 +366,7 @@ func TestUpdateToInvalid(t *testing.T) {
 }
 
 func TestInvalidAvailability(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	s := db.NewFileSet("test", ldb)
 
@@ -419,10 +404,7 @@ func TestInvalidAvailability(t *testing.T) {
 }
 
 func TestGlobalReset(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	m := db.NewFileSet("test", ldb)
 
@@ -460,10 +442,7 @@ func TestGlobalReset(t *testing.T) {
 }
 
 func TestNeed(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	m := db.NewFileSet("test", ldb)
 
@@ -501,10 +480,7 @@ func TestNeed(t *testing.T) {
 }
 
 func TestLocalVersion(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	m := db.NewFileSet("test", ldb)
 
@@ -534,10 +510,7 @@ func TestLocalVersion(t *testing.T) {
 }
 
 func TestListDropFolder(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	s0 := db.NewFileSet("test0", ldb)
 	local1 := []protocol.FileInfo{
@@ -558,7 +531,7 @@ func TestListDropFolder(t *testing.T) {
 	// Check that we have both folders and their data is in the global list
 
 	expectedFolderList := []string{"test0", "test1"}
-	if actualFolderList := db.ListFolders(ldb); !reflect.DeepEqual(actualFolderList, expectedFolderList) {
+	if actualFolderList := ldb.ListFolders(); !reflect.DeepEqual(actualFolderList, expectedFolderList) {
 		t.Fatalf("FolderList mismatch\nE: %v\nA: %v", expectedFolderList, actualFolderList)
 	}
 	if l := len(globalList(s0)); l != 3 {
@@ -573,7 +546,7 @@ func TestListDropFolder(t *testing.T) {
 	db.DropFolder(ldb, "test1")
 
 	expectedFolderList = []string{"test0"}
-	if actualFolderList := db.ListFolders(ldb); !reflect.DeepEqual(actualFolderList, expectedFolderList) {
+	if actualFolderList := ldb.ListFolders(); !reflect.DeepEqual(actualFolderList, expectedFolderList) {
 		t.Fatalf("FolderList mismatch\nE: %v\nA: %v", expectedFolderList, actualFolderList)
 	}
 	if l := len(globalList(s0)); l != 3 {
@@ -585,10 +558,7 @@ func TestListDropFolder(t *testing.T) {
 }
 
 func TestGlobalNeedWithInvalid(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	s := db.NewFileSet("test1", ldb)
 
@@ -625,10 +595,7 @@ func TestGlobalNeedWithInvalid(t *testing.T) {
 }
 
 func TestLongPath(t *testing.T) {
-	ldb, err := leveldb.Open(storage.NewMemStorage(), nil)
-	if err != nil {
-		t.Fatal(err)
-	}
+	ldb := db.OpenMemory()
 
 	s := db.NewFileSet("test", ldb)