CB-9119 Adding lib/retry.js for retrying promise-returning functions. Retrying 'adb install' in emulator.js because it sometimes hangs.

bin/templates/cordova/lib/exec.js

@@ -19,23 +19,50 @@
        under the License.
 */
 
-var child_process = require('child_process'),
-    Q       = require('q');
+var child_process = require("child_process");
+var Q             = require("q");
+
+// constants
+var DEFAULT_MAX_BUFFER = 1024000;
 
 // Takes a command and optional current working directory.
 // Returns a promise that either resolves with the stdout, or
 // rejects with an error message and the stderr.
-module.exports = function(cmd, opt_cwd) {
+//
+// WARNING:
+//         opt_cwd is an artifact of an old design, and must
+//         be removed in the future; the correct solution is
+//         to pass the options object the same way that
+//         child_process.exec expects
+//
+// NOTE:
+//      exec documented here - https://nodejs.org/api/child_process.html#child_process_child_process_exec_command_options_callback
+module.exports = function(cmd, opt_cwd, options) {
+
     var d = Q.defer();
+
+    if (typeof options === "undefined") {
+        options = {};
+    }
+
+    // override cwd to preserve old opt_cwd behavior
+    options.cwd = opt_cwd;
+
+    // set maxBuffer
+    if (typeof options.maxBuffer === "undefined") {
+        options.maxBuffer = DEFAULT_MAX_BUFFER;
+    }
+
     try {
-        child_process.exec(cmd, {cwd: opt_cwd, maxBuffer: 1024000}, function(err, stdout, stderr) {
-            if (err) d.reject('Error executing "' + cmd + '": ' + stderr);
+        child_process.exec(cmd, options, function(err, stdout, stderr) {
+            if (err) d.reject("Error executing \"" + cmd + "\": " + stderr);
             else d.resolve(stdout);
         });
     } catch(e) {
-        console.error('error caught: ' + e);
+        console.error("error caught: " + e);
         d.reject(e);
     }
+
     return d.promise;
 };