The .gitattributes settings will only affect new commits. If this repository has no history published (no others depending on it), you might want to go through the whole history. In Unix/Linux, you can use dos2unix(1) to fix all files in combination with find(1), and using the history rewriting of filter-branch (see the discussion in the git book) you can even clean up the full history of the project.
Use with utmost care, on a fresh clone. Get in contact with anybody who might have a clone, and advise them what you want to do.
For those using v2.16 or better, you can simply use:
git add --renormalize . # Update index with renormalized files
git status # Show the files that will be normalized
git commit -m "Introduce end-of-line normalization"
These directions are straight out of the gitattributes. For older versions, the docs
(prior to v2.12) provide a different answer:
rm .git/index # Remove the index to force git to
git reset # re-scan the working directory
git status # Show files that will be normalized
git add -u
git add .gitattributes
git commit -m "Introduce end-of-line normalization"
Do this sequence after you have edited .gitattributes.
Update
It appears some users have had trouble with the above instructions. Updated docs for gitattributes (2.12 to 2.14) shows a new set of instructions (after editing the .gitattributes files):
git read-tree --empty # Clean index, force re-scan of working directory
git add .
git status # Show files that will be normalized
git commit -m "Introduce end-of-line normalization"
Also, with either solution the files in your working copy still retain their old line endings. If you want to update them, make sure your working tree is clean and use:
git rm --cached -r .
git reset --hard
Now the line endings will be correct in your working tree.
The * text=auto option in .gitattributes leaves the Git repository in an 'illegal state' if it contains files with CRLF (Windows) line endings which are now marked as text (see https://marc.info/?l=git&m=154484903528621&w=2). The standard renormalize option does not work correctly with the LFS filters, so the instructions in the other answers or for example at https://help.github.com/en/articles/dealing-with-line-endings, do not work correctly. Instead these steps worked for us:
Situation:
On Windows
Git repository contained files with both CR and CRLF line endings
Added * text=auto to .gitattributes (so not depended on user having set core.crlf=auto on Windows)
Also changed the -crlf to -text for LFS tracked files, not sure that is needed.
Create a new branch from the branch with the line ending problem (assuming no uncommitted changes there): git checkout -b feature/doing-stuff-fix-eol
Remove the LFS filters from .gitattributes (replace all 'filter=lfs diff=lfs merge=lfs ' with nothing)
Commit and push: git commit -a -m "Disable LFS filters for EOL fix"
Move to non-git folder
Uninstall LFS globally: git lfs uninstall
Create a new repository clone: git clone -b feature/doing-stuff-fix-eol [remote repository url] fix-eol
Normalize the line endings: git add --renormalize . (note the dot to renormalize all files)
Check only the correct files normalized. It should not include files normally handled by LFS!
Commit and push (save the hash): git commit -m "Fix line endings"
Move to non-git folder
Install LFS globally: git lfs install
Go to original repository clone and pull
Checkout your original branch: git checkout feature/doing-stuff
Cherry pick the eol fix commit and push: git cherry-pick [hash]
Delete the eol branch and push
Delete the eol repository clone (or keep around if you need to fix more branches)
Our project initially was made with LF on Mac, but on Windows it was automatically converted to CRLF. We use eslint and it underlined every line of code, until I re-cloned it.