Add cmd/gots-dump tool

This produces output similar to `ots info`, dumping the timestamp tree
of a detached timestamp file.

Author: OttoAllmendinger

Makefile

@@ -1,6 +1,9 @@
-.PHONY: test
+.PHONY: build test
 
 MYPKG=$(shell go list ./... | grep -v /vendor/)
 
+build:
+	go build $(MYPKG)
+
 test:
 	go test $(MYPKG)

cmd/gots-dump/.gitignore

@@ -0,0 +1 @@
+gots-dump

cmd/gots-dump/main.go

@@ -0,0 +1,29 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/BlockchainSource/go-opentimestamps/opentimestamps"
+)
+
+func main() {
+	flag.Parse()
+	path := flag.Arg(0)
+	f, err := os.Open(path)
+	if err != nil {
+		log.Fatalf("error opening file: %v", err)
+	}
+
+	ts, err := opentimestamps.NewDetachedTimestampFile(f)
+	if err != nil {
+		log.Fatalf(
+			"error decoding detached timestamp %s: %v",
+			path, err,
+		)
+	}
+
+	fmt.Println(ts.Dump())
+}