git warnings 'LF will be replaced by CRLF the next time Git touches it' and 'CRLF would be replaced by LF', or whole files showing as changed: how do I set up line ending normalization (.gitattributes, core.autocrlf)?

Cause: Windows editors write CRLF line endings while most repositories store LF. Git's end-of-line conversion (core.autocrlf, core.eol and the text and eol attributes) rewrites endings on add and checkout, and warns when it does. If team members have different settings, or a file was committed with mixed endings, you see these warnings and diffs where every line changed. Fix (best first): 1. Put the policy in the repository so it applies to everyone. Create .gitattributes with * text=auto, and add explicit rules where needed, for example *.sh text eol=lf, *.bat text eol=crlf, and *.png binary (or -text) for non-text files. 2. Normalize files already committed: after adding .gitattributes run git add --renormalize . and review git status and git diff --cached. Commit that change on its own so it is easy to review. 3. Per-user settings only matter when the repository gives no attribute. Common choices: git config --global core.autocrlf true on Windows (LF in the repository, CRLF in the working tree) and core.autocrlf input on Linux or macOS. Note core.eol is ignored when autocrlf is true or input. 4. core.safecrlf set to warn (or true) makes Git tell you, or refuse, when a conversion would not be reversible, which helps find files with mixed endings. 5. Shell scripts with CRLF fail on Linux with errors such as bad interpreter; mark them eol=lf. 6. Teammates should re-checkout or re-clone after the normalization commit to refresh their working trees (commit or stash first). Verify: git add --renormalize . reports nothing further to change, git diff is empty on an untouched checkout, and the warnings no longer appear. Sources: https://git-scm.com/docs/gitattributes https://git-scm.com/docs/git-config