Add gitlab-protocol to config command and schema

res/composer-schema.json

@@ -143,6 +143,10 @@
                         "type": "string"
                     }
                 },
+                "gitlab-protocol": {
+                    "enum": ["git", "http", "https"],
+                    "description": "A protocol to force use of when creating a repository URL for the `source` value of the package metadata. One of `git` or `http`. By default, Composer will generate a git URL for private repositories and http one for public repos."
+                },
                 "bearer": {
                     "type": "object",
                     "description": "A hash of domain name => bearer authentication token, for example {\"example.com\":\"<token>\"}.",

src/Composer/Command/ConfigCommand.php

@@ -330,6 +330,14 @@ EOT
                     return $val;
                 },
             ),
+            'gitlab-protocol' => array(
+                function ($val) {
+                    return in_array($val, array('git', 'http', 'https'), true);
+                },
+                function ($val) {
+                    return $val;
+                },
+            ),
             'store-auths' => array(
                 function ($val) {
                     return in_array($val, array('true', 'false', 'prompt'), true);