diff --git a/.taskcluster.yml b/.taskcluster.yml
index d7b380ae766..2629526ea64 100644
--- a/.taskcluster.yml
+++ b/.taskcluster.yml
@@ -27,6 +27,11 @@ tasks:
             sha256:7471a998e4462638c8d3e2cf0b4a99c9a5c8ca9f2ec0ae01cc069473b35cde10"
         features:
           taskclusterProxy: true
+        artifacts:
+          public/repo.bundle:
+            type: file
+            path: /repo.bundle
+            expires: {$fromNow: '1 day'}
         env:
           GIT_URL: ${event.repository.clone_url}
           TASK_FOR: ${tasks_for}
diff --git a/etc/taskcluster/decision_task.py b/etc/taskcluster/decision_task.py
index 841bc54882c..9500656fb2c 100644
--- a/etc/taskcluster/decision_task.py
+++ b/etc/taskcluster/decision_task.py
@@ -10,6 +10,11 @@ from decisionlib import CONFIG, SHARED
 
 
 def main(task_for):
+    with decisionlib.make_repo_bundle():
+        tasks(task_for)
+
+
+def tasks(task_for):
     if CONFIG.git_ref.startswith("refs/heads/"):
         branch = CONFIG.git_ref[len("refs/heads/"):]
         CONFIG.treeherder_repository_name = "servo-" + (
diff --git a/etc/taskcluster/decisionlib.py b/etc/taskcluster/decisionlib.py
index d556f46139c..e206ae8aa97 100644
--- a/etc/taskcluster/decisionlib.py
+++ b/etc/taskcluster/decisionlib.py
@@ -14,6 +14,7 @@ Project-independent library for Taskcluster decision tasks
 """
 
 import base64
+import contextlib
 import datetime
 import hashlib
 import json
@@ -28,6 +29,7 @@ import taskcluster
 __all__ = [
     "CONFIG", "SHARED", "Task", "DockerWorkerTask",
     "GenericWorkerTask", "WindowsGenericWorkerTask", "MacOsGenericWorkerTask",
+    "make_repo_bundle",
 ]
 
 
@@ -842,3 +844,19 @@ def deindent(string):
 
 def url_basename(url):
     return url.rpartition("/")[-1]
+
+
+@contextlib.contextmanager
+def make_repo_bundle():
+    subprocess.check_call(["git", "config", "user.name", "Decision task"])
+    subprocess.check_call(["git", "config", "user.email", "nobody@mozilla.com"])
+    tree = subprocess.check_output(["git", "show", CONFIG.git_sha, "--pretty=%T", "--no-patch"])
+    message = "Shallow version of commit " + CONFIG.git_sha
+    commit = subprocess.check_output(["git", "commit-tree", tree.strip(), "-m", message])
+    subprocess.check_call(["git", "update-ref", "refs/heads/shallow", commit.strip()])
+    subprocess.check_call(["git", "show-ref"])
+    with subprocess.Popen(["git", "bundle", "create", "../repo.bundle", "refs/heads/shallow"]) as p:
+        yield
+        exit_code = p.wait()
+        if exit_code:
+            sys.exit(exit_code)
diff --git a/etc/taskcluster/mock.py b/etc/taskcluster/mock.py
index 9299c7c84df..cbc495ee5b5 100755
--- a/etc/taskcluster/mock.py
+++ b/etc/taskcluster/mock.py
@@ -39,7 +39,7 @@ class Index:
 
 stringDate = str
 slugId = b"<new id>".lower
-Queue = fromNow = MagicMock()
+sys.exit = Queue = fromNow = MagicMock()
 sys.modules["taskcluster"] = sys.modules[__name__]
 sys.dont_write_bytecode = True
 os.environ.update(**{k: k for k in "TASK_ID TASK_OWNER TASK_SOURCE GIT_URL GIT_SHA".split()})
@@ -48,6 +48,7 @@ os.environ["TASKCLUSTER_ROOT_URL"] = "https://community-tc.services.mozilla.com"
 os.environ["TASKCLUSTER_PROXY_URL"] = "http://taskcluster"
 os.environ["NEW_AMI_WORKER_TYPE"] = "-"
 import decision_task
+decision_task.decisionlib.subprocess = MagicMock()
 
 print("\n# Push:")
 decision_task.main("github-push")