Git ignore & changing the past

Question

I only recently added a .gitignore file to ignore some specific data files in a subdirectory of mine. I'd really like to go back in time and remove them from previous commits/history as well.

Is this easily accomplished? Where/how should I start?

Answer 1

I've just done this and some of the other answers/comments nearly got me there, but I had to make some changes.

I've used filter-branch to introduce my .gitignore file at the start of history, and apply it to all previous commits.

This is the command:

git filter-branch --tree-filter 'git rm --cached -rf . >/dev/null ; cp ~/Desktop/new-gitignore .gitignore ; git add . ; git clean -d -X -f >/dev/null' -- --all

As you can see, it assumes you have a copy of the wanted .gitignore file on your Desktop (~/Desktop/new-gitignore).

I found that only after I've removed and re-added (git rm ..., git add .) all the files would git clean remove all the files that the new .gitignore is telling it to ignore. Notice its not necessary to add the files again after clean, as tree-filter will just commit everything as is.

I've included >/dev/null to reduce the output of the script, but you can safely remove this if you want to see the whole process.