Re-add main.go and add install instruction

Updated .gitignore to alloy cayley to be kept.

.gitignore

@@ -2,5 +2,4 @@
 main
 *.test
 *.peg.go
-cayley
 cayley.cfg

README.md

@@ -52,10 +52,7 @@ Make sure you have the right packages installed. Mostly, this is just Go as a de
 Now you can clone the repository and build the project.
 
 ```bash
-git clone git@github.com:google/cayley.git
-cd cayley
-make deps
-make
+go get github.com/google/cayley/cmd/cayley
 ```
 
 And the `cayley` binary will be built and ready.

cmd/cayley/main.go

@@ -0,0 +1,89 @@
+// Copyright 2014 The Cayley Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"runtime"
+
+	"github.com/barakmich/glog"
+
+	"github.com/google/cayley"
+	"github.com/google/cayley/config"
+	"github.com/google/cayley/graph"
+	"github.com/google/cayley/http"
+)
+
+var tripleFile = flag.String("triples", "", "Triple File to load before going to REPL.")
+var cpuprofile = flag.String("prof", "", "Output profiling file.")
+var queryLanguage = flag.String("query_lang", "gremlin", "Use this parser as the query language.")
+var configFile = flag.String("config", "", "Path to an explicit configuration file.")
+
+func Usage() {
+	fmt.Println("Cayley is a graph store and graph query layer.\n")
+	fmt.Println("Usage:")
+	fmt.Println("  cayley COMMAND [flags]\n")
+	fmt.Println("Commands:")
+	fmt.Println("  init\tCreate an empty database.")
+	fmt.Println("  load\tBulk-load a triple file into the database.")
+	fmt.Println("  http\tServe an HTTP endpoint on the given host and port.")
+	fmt.Println("  repl\tDrop into a REPL of the given query language.")
+	fmt.Println("\nFlags:")
+	flag.Parse()
+	flag.PrintDefaults()
+}
+
+func main() {
+	// No command? It's time for usage.
+	if len(os.Args) == 1 {
+		Usage()
+		os.Exit(1)
+	}
+	cmd := os.Args[1]
+	newargs := make([]string, 0)
+	newargs = append(newargs, os.Args[0])
+	newargs = append(newargs, os.Args[2:]...)
+	os.Args = newargs
+	flag.Parse()
+	var ts graph.TripleStore
+	cfg := config.ParseConfigFromFlagsAndFile(*configFile)
+	if os.Getenv("GOMAXPROCS") == "" {
+		runtime.GOMAXPROCS(runtime.NumCPU())
+		glog.Infoln("Setting GOMAXPROCS to", runtime.NumCPU())
+	} else {
+		glog.Infoln("GOMAXPROCS currently", os.Getenv("GOMAXPROCS"), " -- not adjusting")
+	}
+	switch cmd {
+	case "init":
+		cayley.CayleyInit(cfg, *tripleFile)
+	case "load":
+		ts = cayley.OpenTSFromConfig(cfg)
+		cayley.CayleyLoad(ts, cfg, *tripleFile, false)
+		ts.Close()
+	case "repl":
+		ts = cayley.OpenTSFromConfig(cfg)
+		cayley.CayleyRepl(ts, *queryLanguage, cfg)
+		ts.Close()
+	case "http":
+		ts = cayley.OpenTSFromConfig(cfg)
+		http.CayleyHTTP(ts, cfg)
+		ts.Close()
+	default:
+		fmt.Println("No command", cmd)
+		flag.Usage()
+	}
+}