Initialise spec submodule through composer

Author: alcaeus

.evergreen/config/functions.yml

@@ -4,11 +4,6 @@ functions:
     - command: git.get_project
       params:
         directory: "src"
-    - command: shell.exec
-      params:
-        working_dir: "src"
-        script: |
-          git submodule update --init
     # Make an evergreen exapanstion file with dynamic values
     - command: shell.exec
       params:

CONTRIBUTING.md

@@ -13,7 +13,8 @@ $ composer update
 
 In addition to installing project dependencies, Composer will check that the
 required extension version is installed. Directions for installing the extension
-may be found [here](https://php.net/manual/en/mongodb.installation.php).
+may be found [here](https://php.net/manual/en/mongodb.installation.php). Composer will also install the submodule required for
+running spec tests.
 
 Installation directions for Composer may be found in its
 [Getting Started](https://getcomposer.org/doc/00-intro.md) guide.
@@ -22,11 +23,7 @@ Installation directions for Composer may be found in its
 
 The library's test suite uses [PHPUnit](https://phpunit.de/), which is installed
 through the [PHPUnit Bridge](https://symfony.com/phpunit-bridge) dependency by
-Composer. To run the spec tests, initialize the corresponding Git submodule:
-
-```
-$ git submodule update --init
-```
+Composer.
 
 The test suite may be executed with:
 

composer.json

@@ -39,6 +39,8 @@
         }
     },
     "scripts": {
+        "pre-install-cmd": "git submodule update --init",
+        "pre-update-cmd": "git submodule update --init",
         "bench": "cd benchmark && composer update && vendor/bin/phpbench run --report=aggregate",
         "checks": [
             "@check:cs",