Add the ability to set the development server IP address from gulp

CONTRIBUTING.md

@@ -160,6 +160,8 @@ in the [`babybuddy/management/commands`](babybuddy/management/commands) folder.
 #### `gulp`
 
 Executes the `build` and `watch` commands and runs Django's development server.
+This command also accepts the special parameter `--ip` for setting the
+development server IP address. See [`gulp runserver`](#runserver) for details.
 
 #### `build`
 
@@ -240,8 +242,12 @@ fake data.
 
 #### `runserver`
 
-Executes Django's `runserver` management task. Gulp also passes along
+Executes Django's `runserver` management task. Gulp passes non-overlapping
-non-overlapping arguments for this command.
+arguments for this command.
+
+A special parameter, `--ip`, is also available to set the IP for the server.
+E.g execute `gulp runserver --ip 0.0.0.0:8000` to make the server available to
+other devices on your local network.
 
 #### `scripts`
 

gulpfile.js

@@ -216,7 +216,30 @@ gulp.task('clean', clean);
 
 gulp.task('runserver', function(cb) {
     var command = ['run', 'python', 'manage.py', 'runserver'];
-    command = command.concat(process.argv.splice(3));
+
+    /**
+     * Process any parameters. Any arguments found here will be removed from
+     * the parameters list so other parameters continue to be passed to the
+     * command.
+     **/
+    var parameters = process.argv.splice(2);
+    for (var i = 0; i < parameters.length; i++) {
+        /* May be included because this is the default gulp command. */
+        if (parameters[i] === 'runserver') {
+            delete parameters[i];
+        }
+        /* "--ip" parameter to set the server IP address. */
+        else if (parameters[i] === '--ip') {
+            command.push(parameters[i+1]);
+            delete parameters[i];
+            delete parameters[i+1];
+            i++;
+        }
+    }
+
+    /* Add parameters to command, removing empty values. */
+    command = command.concat(parameters.filter(String));
+
     spawn('pipenv', command, { stdio: 'inherit' }).on('exit', cb);
 });