use .git-blame-ignore-revs

If there is a .git-blame-ignore-revs in a repo, issue the following command

git -C repo config --local  blame.ignoreRevsFile .git-blame-ignore-revs

The disadvantage is that if one checks out an old version without the file git blame will not work.

We could also create an empty file but then once a file is added, pulling will be an issue