layout.conf: require cache-format now

Since we've updated all our overlays to turn this on, enforce it with
new ones to make sure it stays on everywhere.

BUG=b:242194202
TEST=CQ passes

Change-Id: Ic09907cfb675a822df8d6ef2254196257c348120
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/repohooks/+/3898324
Tested-by: Mike Frysinger <vapier@chromium.org>
Auto-Submit: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Jack Rosenthal <jrosenth@chromium.org>
diff --git a/pre-upload.py b/pre-upload.py
index 167eeaa..b2f4923 100755
--- a/pre-upload.py
+++ b/pre-upload.py
@@ -2265,8 +2265,7 @@
 
         # Require people to set specific values all the time.
         settings = (
-            # TODO: Enable this for everyone.  http://crbug.com/408038
-            # ('fast caching', 'cache-format = md5-dict'),
+            ('fast caching', 'cache-format = md5-dict'),
             ("fast manifests", "thin-manifests = true"),
             (
                 "extra features",
diff --git a/pre-upload_unittest.py b/pre-upload_unittest.py
index 5e0655a..6b4f784 100755
--- a/pre-upload_unittest.py
+++ b/pre-upload_unittest.py
@@ -1838,6 +1838,7 @@
     def GetLayoutConf(self, filters=()):
         """Return a valid layout.conf with |filters| lines removed."""
         all_lines = [
+            "cache-format = md5-dict",
             "masters = portage-stable chromiumos",  # nocheck
             "profile-formats = portage-2 profile-default-eapi",
             "profile_eapi_when_unspecified = 5-progress",