Search engine indexes old versions

I've noticed often that when I google for CIF documentation (I find it faster than using the Table of Contents), it links to a specific version page.

For example when I google ESCET CIF documentation, the first hit links to https://www.eclipse.org/escet/v0.1/cifc. Ideally, we want only links to the non-version pages.

I've read that this can be accomplished by creating a robots.txt. See E.g., this issue or this issue, and this example file.