auto management of dependencies temporarily needed to build plugin and transformer

migrations; new test showing it is working with external transformers runs
properly when migrations were manually performed but still need
to test automated migration management

utils/utils.go

@@ -17,10 +17,14 @@
 package utils
 
 import (
+	"io"
 	"math/big"
 	"os"
 	"path/filepath"
+	"strings"
+	"syscall"
 
+	"github.com/mitchellh/go-homedir"
 	log "github.com/sirupsen/logrus"
 
 	"github.com/vulcanize/vulcanizedb/pkg/config"
@@ -80,3 +84,54 @@ func RequestedBlockNumber(blockNumber *int64) *big.Int {
 	}
 	return _blockNumber
 }
+
+func CleanPath(str string) (string, error) {
+	path, err := homedir.Expand(filepath.Clean(str))
+	if err != nil {
+		return "", err
+	}
+	if strings.Contains(path, "$GOPATH") {
+		env := os.Getenv("GOPATH")
+		spl := strings.Split(path, "$GOPATH")[1]
+		path = filepath.Join(env, spl)
+	}
+
+	return path, nil
+}
+
+func ClearFiles(files ...string) error {
+	for _, file := range files {
+		if _, err := os.Stat(file); err == nil {
+			err = os.Remove(file)
+			if err != nil {
+				return err
+			}
+		} else if os.IsNotExist(err) {
+			// fall through
+		} else {
+			return err
+		}
+	}
+
+	return nil
+}
+
+func CopyFile(src, dst string) error {
+	in, err := os.Open(src)
+	if err != nil {
+		return err
+	}
+	defer in.Close()
+
+	out, err := os.OpenFile(dst, syscall.O_CREAT|syscall.O_EXCL, os.FileMode(0666)) // Doesn't overwrite files
+	if err != nil {
+		return err
+	}
+	defer out.Close()
+
+	_, err = io.Copy(out, in)
+	if err != nil {
+		return err
+	}
+	return out.Close()
+}