etcdmain: let user provide a name w/o initial-cluster update

Currently this doesn't work if a user wants to try out a single machine
cluster but change the name for whatever reason. This is because the
name is always "default" and the

```
./bin/etcd -name 'baz'
```

This solves our problem on CoreOS where the default is `ETCD_NAME=%m`.

etcdmain/config.go

@@ -41,6 +41,8 @@ const (
 
 	clusterStateFlagNew      = "new"
 	clusterStateFlagExisting = "existing"
+
+	defaultName = "default"
 )
 
 var (
@@ -137,7 +139,7 @@ func NewConfig() *config {
 	fs.Var(flags.NewURLsValue("http://localhost:2379,http://localhost:4001"), "listen-client-urls", "List of URLs to listen on for client traffic")
 	fs.UintVar(&cfg.maxSnapFiles, "max-snapshots", defaultMaxSnapshots, "Maximum number of snapshot files to retain (0 is unlimited)")
 	fs.UintVar(&cfg.maxWalFiles, "max-wals", defaultMaxWALs, "Maximum number of wal files to retain (0 is unlimited)")
-	fs.StringVar(&cfg.name, "name", "default", "Unique human-readable name for this node")
+	fs.StringVar(&cfg.name, "name", defaultName, "Unique human-readable name for this node")
 	fs.Uint64Var(&cfg.snapCount, "snapshot-count", etcdserver.DefaultSnapCount, "Number of committed transactions to trigger a snapshot")
 	fs.UintVar(&cfg.TickMs, "heartbeat-interval", 100, "Time (in milliseconds) of a heartbeat interval.")
 	fs.UintVar(&cfg.ElectionMs, "election-timeout", 1000, "Time (in milliseconds) for an election to timeout.")
@@ -153,7 +155,7 @@ func NewConfig() *config {
 	}
 	fs.StringVar(&cfg.dproxy, "discovery-proxy", "", "HTTP proxy to use for traffic to discovery service")
 	fs.StringVar(&cfg.dnsCluster, "discovery-srv", "", "DNS domain used to bootstrap initial cluster")
-	fs.StringVar(&cfg.initialCluster, "initial-cluster", "default=http://localhost:2380,default=http://localhost:7001", "Initial cluster configuration for bootstrapping")
+	fs.StringVar(&cfg.initialCluster, "initial-cluster", initialClusterFromName(defaultName), "Initial cluster configuration for bootstrapping")
 	fs.StringVar(&cfg.initialClusterToken, "initial-cluster-token", "etcd-cluster", "Initial cluster token for the etcd cluster during bootstrap")
 	fs.Var(cfg.clusterState, "initial-cluster-state", "Initial cluster configuration for bootstrapping")
 	if err := cfg.clusterState.Set(clusterStateFlagNew); err != nil {
@@ -266,6 +268,14 @@ func (cfg *config) Parse(arguments []string) error {
 	return nil
 }
 
+func initialClusterFromName(name string) string {
+	n := name
+	if name == "" {
+		n = defaultName
+	}
+	return fmt.Sprintf("%s=http://localhost:2380,%s=http://localhost:7001", n, n)
+}
+
 func (cfg *config) resolveUrls() error {
 	return netutil.ResolveTCPAddrs(cfg.lpurls, cfg.apurls, cfg.lcurls, cfg.acurls)
 }

etcdmain/etcd.go

@@ -62,6 +62,10 @@ func Main() {
 
 	var stopped <-chan struct{}
 
+	if cfg.name != defaultName && cfg.initialCluster == initialClusterFromName(defaultName) {
+		cfg.initialCluster = initialClusterFromName(cfg.name)
+	}
+
 	if cfg.dir == "" {
 		cfg.dir = fmt.Sprintf("%v.etcd", cfg.name)
 		log.Printf("etcd: no data-dir provided, using default data-dir ./%s", cfg.dir)