error: cannot lock ref

Line ending mismatches are a persistent source of REF LOCK ERROR in cross-platform teams. Windows uses CRLF (\r\n), Linux and macOS use LF (\n). Without coordination, every file shows as modified after checkout on a different OS. The authoritative fix is a .gitattributes file committed to the repository root: * text=auto normalizes all text files to LF in the repository and converts to the platform's line ending on checkout. For shell scripts and executables that must always have LF (even on Windows), use *.sh text eol=lf. For files that should always have CRLF (Windows batch scripts), use *.bat text eol=crlf. Git's core.autocrlf setting is an alternative but is per-machine rather than per-repository — committing .gitattributes enforces consistency for the whole team regardless of individual settings. After adding .gitattributes, normalize existing files with git add --renormalize . to fix line endings in the index without modifying working tree files.