scripts: Keep the .git in docs

Signed-off-by: Ce Gao <ce.gao@outlook.com>

Author: gaocegege

scripts/generate-reference.sh

@@ -3,8 +3,10 @@
 ROOT=$(dirname "${BASH_SOURCE}")/..
 
 cd ${ROOT}
-rm -rf docs
+mv docs/.git cache.git.dir
+rm -rf docs/
 mkdir -p docs/reference
+mv cache.git.dir docs/.git
 cp -r content/* docs/
 exec python3 ./src/generate.py $@
 cd - > /dev/null