cmd/ent: replace entc with ent (#989)

See #981

cmd/internal/base/packages.go

@@ -0,0 +1,55 @@
+// Copyright 2019-present Facebook Inc. All rights reserved.
+// This source code is licensed under the Apache 2.0 license found
+// in the LICENSE file in the root directory of this source tree.
+
+package base
+
+import (
+	"fmt"
+	"os"
+	"path"
+	"path/filepath"
+
+	"golang.org/x/tools/go/packages"
+)
+
+// DefaultConfig for loading Go base.
+var DefaultConfig = &packages.Config{Mode: packages.NeedName}
+
+// PkgPath returns the Go package name for given target path.
+// Even if the existing path is not exist yet in the filesystem.
+//
+// If base.Config is nil, DefaultConfig will be used to load base.
+func PkgPath(config *packages.Config, target string) (string, error) {
+	if config == nil {
+		config = DefaultConfig
+	}
+	pathCheck, err := filepath.Abs(target)
+	if err != nil {
+		return "", err
+	}
+	var parts []string
+	if _, err := os.Stat(pathCheck); os.IsNotExist(err) {
+		parts = append(parts, filepath.Base(pathCheck))
+		pathCheck = filepath.Dir(pathCheck)
+	}
+	// Try maximum 2 directories above the given
+	// target to find the root package or module.
+	for i := 0; i < 2; i++ {
+		pkgs, err := packages.Load(config, pathCheck)
+		if err != nil {
+			return "", fmt.Errorf("load package info: %v", err)
+		}
+		if len(pkgs) == 0 || len(pkgs[0].Errors) != 0 {
+			parts = append(parts, filepath.Base(pathCheck))
+			pathCheck = filepath.Dir(pathCheck)
+			continue
+		}
+		pkgPath := pkgs[0].PkgPath
+		for j := len(parts) - 1; j >= 0; j-- {
+			pkgPath = path.Join(pkgPath, parts[j])
+		}
+		return pkgPath, nil
+	}
+	return "", fmt.Errorf("root package or module was not found for: %s", target)
+}