Vendor godep v79 and use it

vendor/github.com/tools/godep/diff.go

@@ -0,0 +1,74 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"log"
+
+	"github.com/pmezard/go-difflib/difflib"
+)
+
+var cmdDiff = &Command{
+	Name:  "diff",
+	Short: "shows the diff between current and previously saved set of dependencies",
+	Long: `
+Shows the difference, in a unified diff format, between the
+current set of dependencies and those generated on a
+previous 'go save' execution.
+`,
+	Run:          runDiff,
+	OnlyInGOPATH: true,
+}
+
+func runDiff(cmd *Command, args []string) {
+	gold, err := loadDefaultGodepsFile()
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	pkgs := []string{"."}
+	dot, err := LoadPackages(pkgs...)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	gnew := &Godeps{
+		ImportPath: dot[0].ImportPath,
+		GoVersion:  gold.GoVersion,
+	}
+
+	err = gnew.fill(dot, dot[0].ImportPath)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	diff, err := diffStr(&gold, gnew)
+	if err != nil {
+		log.Fatalln(err)
+	}
+	fmt.Println(diff)
+}
+
+// diffStr returns a unified diff string of two Godeps.
+func diffStr(a, b *Godeps) (string, error) {
+	var ab, bb bytes.Buffer
+
+	_, err := a.writeTo(&ab)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	_, err = b.writeTo(&bb)
+	if err != nil {
+		log.Fatalln(err)
+	}
+
+	diff := difflib.UnifiedDiff{
+		A:        difflib.SplitLines(ab.String()),
+		B:        difflib.SplitLines(bb.String()),
+		FromFile: b.file(),
+		ToFile:   "$GOPATH",
+		Context:  10,
+	}
+	return difflib.GetUnifiedDiffString(diff)
+}