🐛 Bug - biome format fails on every file for Windows devs (CRLF vs lineEnding lf) #2716

Pain

On a Windows checkout, biome format . fails on effectively the whole repo:

Checked 672 files in 1639ms. No fixes applied.
Found 850 errors.

Figure: every diagnostic is a ␍ (carriage return), including in files nobody has touched

biome.json sets formatter.lineEnding: "lf", but Git for Windows checks files out with CRLF by default (core.autocrlf=true) and there is no .gitattributes normalising text files. So the working tree is CRLF and Biome wants LF, on every line of every file.

The practical effect for Windows devs:

• biome format is unusable as a check — the signal is 100% noise
• running biome format --write "fixes" it by rewriting all 677 files to LF, which produces an enormous diff and gets undone on the next checkout
• a real formatting mistake is invisible among the CRLF diagnostics

CI is not affected (Linux checks out LF), and biome format isn't run in CI anyway — which is why this has gone unnoticed.

Acceptance Criteria

1. biome format . passes on a fresh clone on Windows, macOS and Linux.
2. Line endings are consistent across platforms and don't flip back on checkout.
3. The one-off renormalisation is its own commit and doesn't pollute git blame.

Reproduce Steps

1. Clone the repo on Windows with default Git settings (core.autocrlf=true).
2. Run npx biome format ..
3. Observe ~850 errors, all of them ␍, across files you have never edited.

Suggested fix

Add a .gitattributes with * text=auto eol=lf so every platform gets LF in the working tree, then renormalise once:

git add --renormalize .

Keep that renormalisation as a single isolated commit and add its SHA to .git-blame-ignore-revs, so it doesn't show up as the last author of every line.

Out of scope, but worth knowing

biome lint . currently reports 183 errors and 5725 warnings repo-wide. Adding a lint gate to CI is a separate, much larger piece of work — this PBI is only about making the formatter usable.