Add line ending fixer

Author: jakebailey

.editorconfig

@@ -0,0 +1,19 @@
+root = true
+
+[*]
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[tsc/testdata/**]
+end_of_line = unset
+charset = unset
+trim_trailing_whitespace = unset
+insert_final_newline = unset
+
+[tsc/internal/locale/lcl/**]
+end_of_line = unset
+charset = unset
+trim_trailing_whitespace = unset
+insert_final_newline = unset

Herebyfile.mjs

@@ -1269,6 +1269,46 @@ export const format = task({
 
 async function runFormat() {
     await $`dprint fmt`;
+    await fixLineEndings();
+}
+
+const lineEndingExclusions = [
+    ":(exclude)tsc/testdata/**",
+    // TODO: Remove this exclusion when this directory is converted or removed.
+    ":(exclude)tsc/internal/locale/lcl/**",
+];
+
+export const fixLineEndingsTask = task({
+    name: "fix:line-endings",
+    description: "Converts tracked files that Git expects to use LF.",
+    run: fixLineEndings,
+});
+
+async function fixLineEndings() {
+    const result = await _$`git ls-files --eol -z -- . ${lineEndingExclusions}`;
+    const files = [];
+    for (const record of result.stdout.split("\0")) {
+        if (!record) {
+            continue;
+        }
+        const separator = record.indexOf("\t");
+        assert(separator !== -1);
+        const eolInfo = record.slice(0, separator);
+        if (!/\bw\/(?:crlf|mixed)\b/.test(eolInfo) || !eolInfo.includes("eol=lf")) {
+            continue;
+        }
+        files.push(record.slice(separator + 1));
+    }
+
+    await Promise.all(files.map(async file => {
+        const contents = await fs.promises.readFile(file);
+        const normalized = Buffer.from(contents.toString("latin1").replaceAll("\r\n", "\n"), "latin1");
+        await fs.promises.writeFile(file, normalized);
+    }));
+
+    if (files.length) {
+        console.log(`Converted ${files.length} file(s) to LF.`);
+    }
 }
 
 export const checkFormat = task({
@@ -1281,12 +1321,7 @@ export const checkFormat = task({
 });
 
 async function checkLineEndings() {
-    const exclusions = [
-        ":(exclude)tsc/testdata/**",
-        // TODO: Remove this exclusion when this directory is converted or removed.
-        ":(exclude)tsc/internal/locale/lcl/**",
-    ];
-    const result = await _$({ reject: false })`git grep --cached -Il ${"\r"} -- . ${exclusions}`;
+    const result = await _$({ reject: false })`git grep --cached -Il ${"\r"} -- . ${lineEndingExclusions}`;
     if (result.exitCode === 1) {
         return;
     }