debugger: don't spawn child process in remote mode

When debug in remote mode with host:port or pid, the interface
spawn child process also. If the debugger agent is running, will
get following output:

```
< Error: listen EADDRINUSE :::5858
<     at Object.exports._errnoException (util.js:734:11)
<     at exports._exceptionWithHostPort (util.js:757:20)
<     at Agent.Server._listen2 (net.js:1155:14)
<     at listen (net.js:1181:10)
<     at Agent.Server.listen (net.js:1268:5)
<     at Object.start (_debug_agent.js:21:9)
<     at startup (node.js:68:9)
<     at node.js:799:3
```

This fix won't spawn child process and no more error message was
shown.

When use `iojs debug`, the tip information just like this:

```
Usage: iojs debug script.js
```

This fix will display the advance usage also:

```
Usage: iojs debug script.js
       iojs debug <host>:<port>
       iojs debug -p <pid>
```

Fixes: https://github.com/iojs/io.js/issues/889
PR-URL: https://github.com/iojs/io.js/pull/1282
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

1 files changed, 52 insertions, 0 deletions

diff --git a/test/debugger/test-debugger-remote.js b/test/debugger/test-debugger-remote.js
new file mode 100644
index 0000000000..641199a171
--- /dev/null
+++ b/test/debugger/test-debugger-remote.js
@@ -0,0 +1,52 @@
+var common = require('../common');
+var assert = require('assert');
+var spawn = require('child_process').spawn;
+
+var port = common.PORT + 1337;
+var buffer = '';
+var expected = [];
+var scriptToDebug = common.fixturesDir + '/empty.js';
+
+function fail() {
+  assert(0); // `iojs --debug-brk script.js` should not quit
+}
+
+// running with debug agent
+var child = spawn(process.execPath, ['--debug-brk=5959', scriptToDebug]);
+
+console.error(process.execPath, '--debug-brk=5959', scriptToDebug);
+
+// connect to debug agent
+var interfacer = spawn(process.execPath, ['debug', 'localhost:5959']);
+
+console.error(process.execPath, 'debug', 'localhost:5959');
+interfacer.stdout.setEncoding('utf-8');
+interfacer.stdout.on('data', function(data) {
+  data = (buffer + data).split('\n');
+  buffer = data.pop();
+  data.forEach(function(line) {
+    interfacer.emit('line', line);
+  });
+});
+
+interfacer.on('line', function(line) {
+  line = line.replace(/^(debug> *)+/, '');
+  console.log(line);
+  var expected = '\bconnecting to localhost:5959 ... ok';
+  assert.ok(expected == line, 'Got unexpected line: ' + line);
+});
+
+// give iojs time to start up the debugger
+setTimeout(function() {
+  child.removeListener('exit', fail);
+  child.kill();
+  interfacer.removeListener('exit', fail);
+  interfacer.kill();
+}, 2000);
+
+process.on('exit', function() {
+  assert(child.killed);
+  assert(interfacer.killed);
+});
+
+interfacer.stderr.pipe(process.stderr);