combine: backend to combine multiple remotes in one directory tree

Fixes #5600

backend/combine/combine_internal_test.go

@@ -0,0 +1,94 @@
+package combine
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestAdjustmentDo(t *testing.T) {
+	for _, test := range []struct {
+		root       string
+		mountpoint string
+		in         string
+		want       string
+		wantErr    error
+	}{
+		{
+			root:       "",
+			mountpoint: "mountpoint",
+			in:         "path/to/file.txt",
+			want:       "mountpoint/path/to/file.txt",
+		},
+		{
+			root:       "mountpoint",
+			mountpoint: "mountpoint",
+			in:         "path/to/file.txt",
+			want:       "path/to/file.txt",
+		},
+		{
+			root:       "mountpoint/path",
+			mountpoint: "mountpoint",
+			in:         "path/to/file.txt",
+			want:       "to/file.txt",
+		},
+		{
+			root:       "mountpoint/path",
+			mountpoint: "mountpoint",
+			in:         "wrongpath/to/file.txt",
+			want:       "",
+			wantErr:    errNotUnderRoot,
+		},
+	} {
+		what := fmt.Sprintf("%+v", test)
+		a := newAdjustment(test.root, test.mountpoint)
+		got, gotErr := a.do(test.in)
+		assert.Equal(t, test.wantErr, gotErr)
+		assert.Equal(t, test.want, got, what)
+	}
+
+}
+
+func TestAdjustmentUndo(t *testing.T) {
+	for _, test := range []struct {
+		root       string
+		mountpoint string
+		in         string
+		want       string
+		wantErr    error
+	}{
+		{
+			root:       "",
+			mountpoint: "mountpoint",
+			in:         "mountpoint/path/to/file.txt",
+			want:       "path/to/file.txt",
+		},
+		{
+			root:       "mountpoint",
+			mountpoint: "mountpoint",
+			in:         "path/to/file.txt",
+			want:       "path/to/file.txt",
+		},
+		{
+			root:       "mountpoint/path",
+			mountpoint: "mountpoint",
+			in:         "to/file.txt",
+			want:       "path/to/file.txt",
+		},
+		{
+			root:       "wrongmountpoint/path",
+			mountpoint: "mountpoint",
+			in:         "to/file.txt",
+			want:       "",
+			wantErr:    errNotUnderRoot,
+		},
+	} {
+		what := fmt.Sprintf("%+v", test)
+		a := newAdjustment(test.root, test.mountpoint)
+		got, gotErr := a.undo(test.in)
+		assert.Equal(t, test.wantErr, gotErr)
+		assert.Equal(t, test.want, got, what)
+	}
+
+}