config+cmd/lncli: add flag to specify the base dir for lnd

In this commit, we introduce a new flag `--lnddir` that allows us to
set a different base directory, other than the OS specific application
data directory, for all related lnd files and directories.

cmd/lncli/main.go

@@ -28,9 +28,9 @@ const (
 )
 
 var (
-	lndHomeDir          = btcutil.AppDataDir("lnd", false)
-	defaultTLSCertPath  = filepath.Join(lndHomeDir, defaultTLSCertFilename)
-	defaultMacaroonPath = filepath.Join(lndHomeDir, defaultMacaroonFilename)
+	defaultLndDir       = btcutil.AppDataDir("lnd", false)
+	defaultTLSCertPath  = filepath.Join(defaultLndDir, defaultTLSCertFilename)
+	defaultMacaroonPath = filepath.Join(defaultLndDir, defaultMacaroonFilename)
 )
 
 func fatal(err error) {
@@ -59,6 +59,27 @@ func getClient(ctx *cli.Context) (lnrpc.LightningClient, func()) {
 }
 
 func getClientConn(ctx *cli.Context, skipMacaroons bool) *grpc.ClientConn {
+	lndDir := cleanAndExpandPath(ctx.GlobalString("lnddir"))
+	if lndDir != defaultLndDir {
+		// If a custom lnd directory was set, we'll also check if custom
+		// paths for the TLS cert and macaroon file were set as well. If
+		// not, we'll override their paths so they can be found within
+		// the custom lnd directory set. This allows us to set a custom
+		// lnd directory, along with custom paths to the TLS cert and
+		// macaroon file.
+		tlsCertPath := cleanAndExpandPath(ctx.GlobalString("tlscertpath"))
+		if tlsCertPath == defaultTLSCertPath {
+			ctx.GlobalSet("tlscertpath",
+				filepath.Join(lndDir, defaultTLSCertFilename))
+		}
+
+		macPath := cleanAndExpandPath(ctx.GlobalString("macaroonpath"))
+		if macPath == defaultMacaroonPath {
+			ctx.GlobalSet("no-macaroons",
+				filepath.Join(lndDir, defaultMacaroonFilename))
+		}
+	}
+
 	// Load the specified TLS certificate and build transport credentials
 	// with it.
 	tlsCertPath := cleanAndExpandPath(ctx.GlobalString("tlscertpath"))
@@ -136,6 +157,11 @@ func main() {
 			Value: "localhost:10009",
 			Usage: "host:port of ln daemon",
 		},
+		cli.StringFlag{
+			Name:  "lnddir",
+			Value: defaultLndDir,
+			Usage: "path to lnd's base directory",
+		},
 		cli.StringFlag{
 			Name:  "tlscertpath",
 			Value: defaultTLSCertPath,
@@ -210,7 +236,7 @@ func main() {
 func cleanAndExpandPath(path string) string {
 	// Expand initial ~ to OS specific home directory.
 	if strings.HasPrefix(path, "~") {
-		homeDir := filepath.Dir(lndHomeDir)
+		homeDir := filepath.Dir(defaultLndDir)
 		path = strings.Replace(path, "~", homeDir, 1)
 	}