diff --git a/db/bitclust.rev b/db/bitclust.rev
new file mode 100644
index 0000000000..b0b23ed41d
--- /dev/null
+++ b/db/bitclust.rev
@@ -0,0 +1 @@
+102b5559c7723d39263e0480bb0518ca3000ed3c
diff --git a/db/doctree.rev b/db/doctree.rev
new file mode 100644
index 0000000000..7e00f6e97e
--- /dev/null
+++ b/db/doctree.rev
@@ -0,0 +1 @@
+c0d22f34ed2ab0b0f0dd65e5f6dace30260dbbac
diff --git a/generate.sh b/generate.sh
index a0d08012ba..721affd7ea 100755
--- a/generate.sh
+++ b/generate.sh
@@ -19,6 +19,14 @@ else
     git clone --depth 1 https://github.com/rurema/doctree repos/doctree
 fi
 
+git -C repos/bitclust rev-parse HEAD > db/bitclust.rev
+git -C repos/doctree rev-parse HEAD > db/doctree.rev
+
+if [ -z "$(git status -s db/*.rev)" ]; then
+    echo do nothing because bitclust and doctree are same revisions
+    exit
+fi
+
 time docker compose build rurema
 
 time docker compose run --rm rurema ls -al