diff --git a/gogsmaker.py b/gogsmaker.py
index e8e7f4a..e7bd7d3 100644
--- a/gogsmaker.py
+++ b/gogsmaker.py
@@ -2,16 +2,92 @@
 
 A webhook-handler for Gogs running `make` when needed. """
 
+import os
+import subprocess
 from flask import Flask, request
-from .settings import HOOKS
+from . import settings
 
 app = Flask(__name__)
 
 
+class UnmonitoredRepository(Exception):
+    pass
+
+
+class GitError(Exception):
+    def __init__(self, what):
+        self.what = what
+
+    def __str__(self):
+        return self.what
+
+
+def get_hook(url):
+    ''' Get the hook matching an URL, or raise UnmonitoredRepository '''
+    for hook in settings.HOOKS:
+        if hook['url'] == url:
+            return hook
+    raise UnmonitoredRepository
+
+
+def repo_path(hook):
+    ''' Get the path at which the hook's repo is cloned '''
+    return os.path.join(settings.CLONE_ROOT, hook['name'])
+
+
+def update_repo(hook, clone_url):
+    ''' Update (or clone) the given repository. May raise GitError. '''
+    path = repo_path(hook)
+    if os.path.isdir(os.path.join(path, '.git')):  # Repo is already cloned
+        try:
+            subprocess.run(['git', 'clone', clone_url, path], check=True)
+        except subprocess.CalledProcessError:
+            raise GitError("Cannot clone {}".format(clone_url))
+
+    else:  # Simply update
+        try:
+            subprocess.run(['git', '-C', path, 'reset', '--hard'],
+                           check=True)  # Just in case.
+            subprocess.run(['git', '-C', path, 'pull'], check=True)
+        except subprocess.CalledProcessError:
+            raise GitError("Cannot pull {}".format(hook['name']))
+
+
+def gogs_payload(required):
+    def wrapper(fct):
+        payload = request.json
+        if payload is None:
+            return 'Expected json\n', 415
+
+        for field in required + ['repository/html_url']:
+            path = field.split('/')
+            explore = payload
+            for section in path:
+                if section not in explore:
+                    return (
+                        'Invalid json: missing {}\n'.format('/'.join(path)),
+                        400)
+                explore = explore[section]
+
+        try:
+            hook = get_hook(payload['repository']['html_url'])
+        except UnmonitoredRepository:
+            return 'Unmonitored repository\n', 403
+
+        return fct(payload, hook)
+    return wrapper
+
+
 @app.route('/', methods=['POST'])
-def view_root():
-    payload = request.json
-    if payload is None:
-        return 'Expected json\n', 415
-    print(payload)
+@gogs_payload(['repository/clone_url'])
+def view_root(payload, hook):
+    clone_url = payload['repository']['clone_url']
+
+    try:
+        update_repo(hook, clone_url)
+    except GitError as error:
+        return 'Git error: {}\n'.format(error), 500
+
+    # TODO: make
+
     return 'OK\n', 200
diff --git a/settings.default.py b/settings.default.py
index e726f26..6a684f9 100644
--- a/settings.default.py
+++ b/settings.default.py
@@ -14,3 +14,6 @@ HOOKS = [
         'targets': ['all'],
     },
 ]
+
+# Directory in which the repositories are cloned
+CLONE_ROOT = 'repos'