2 files changed, 99 insertions, 0 deletions
diff --git a/src/cmd/buildid/buildid.go b/src/cmd/buildid/buildid.go
new file mode 100644
index 0000000..72ad80d
--- /dev/null
+++ b/src/cmd/buildid/buildid.go
@@ -0,0 +1,80 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+	"strings"
+
+	"cmd/internal/buildid"
+)
+
+func usage() {
+	fmt.Fprintf(os.Stderr, "usage: go tool buildid [-w] file\n")
+	flag.PrintDefaults()
+	os.Exit(2)
+}
+
+var wflag = flag.Bool("w", false, "write build ID")
+
+func main() {
+	log.SetPrefix("buildid: ")
+	log.SetFlags(0)
+	flag.Usage = usage
+	flag.Parse()
+	if flag.NArg() != 1 {
+		usage()
+	}
+
+	file := flag.Arg(0)
+	id, err := buildid.ReadFile(file)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if !*wflag {
+		fmt.Printf("%s\n", id)
+		return
+	}
+
+	// Keep in sync with src/cmd/go/internal/work/buildid.go:updateBuildID
+
+	f, err := os.Open(file)
+	if err != nil {
+		log.Fatal(err)
+	}
+	matches, hash, err := buildid.FindAndHash(f, id, 0)
+	f.Close()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// <= go 1.7 doesn't embed the contentID or actionID, so no slash is present
+	if !strings.Contains(id, "/") {
+		log.Fatalf("%s: build ID is a legacy format...binary too old for this tool", file)
+	}
+
+	newID := id[:strings.LastIndex(id, "/")] + "/" + buildid.HashToString(hash)
+	if len(newID) != len(id) {
+		log.Fatalf("%s: build ID length mismatch %q vs %q", file, id, newID)
+	}
+
+	if len(matches) == 0 {
+		return
+	}
+
+	f, err = os.OpenFile(file, os.O_RDWR, 0)
+	if err != nil {
+		log.Fatal(err)
+	}
+	if err := buildid.Rewrite(f, matches, newID); err != nil {
+		log.Fatal(err)
+	}
+	if err := f.Close(); err != nil {
+		log.Fatal(err)
+	}
+}
diff --git a/src/cmd/buildid/doc.go b/src/cmd/buildid/doc.go
new file mode 100644
index 0000000..a554d79
--- /dev/null
+++ b/src/cmd/buildid/doc.go
@@ -0,0 +1,19 @@
+// Copyright 2017 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+/*
+Buildid displays or updates the build ID stored in a Go package or binary.
+
+Usage:
+
+	go tool buildid [-w] file
+
+By default, buildid prints the build ID found in the named file.
+If the -w option is given, buildid rewrites the build ID found in
+the file to accurately record a content hash of the file.
+
+This tool is only intended for use by the go command or
+other build systems.
+*/
+package main