fix: Windows path handling with Cygwin, WSL, Git Bash

Author: edemaine

CHANGELOG.md

@@ -10,6 +10,8 @@ All notable user-visible changes to Hunk are documented in this file.
 
 ### Fixed
 
+- Fixed Windows launches from Cygwin, Git Bash, and WSL-style VCS paths by normalizing Unix-style repo roots before reusing them as subprocess working directories or filesystem roots.
+
 ## [0.15.1] - 2026-06-09
 
 ### Fixed

src/core/git.ts

@@ -3,6 +3,7 @@ import { join } from "node:path";
 import { HunkUserError } from "./errors";
 import { escapeUntrackedPatchPath } from "./patch/normalize";
 import type { VcsCommandInput, ShowCommandInput, StashShowCommandInput } from "./types";
+import { normalizeWindowsPath } from "../lib/windowsPath";
 
 export type GitBackedInput = VcsCommandInput | ShowCommandInput | StashShowCommandInput;
 
@@ -642,11 +643,12 @@ export function resolveGitRepoRoot(
   input: GitBackedInput,
   options: Omit<RunGitTextOptions, "input" | "args"> = {},
 ) {
-  return runGitText({
+  const repoRoot = runGitText({
     input,
     args: ["rev-parse", "--show-toplevel"],
     ...options,
   }).trim();
+  return normalizeWindowsPath(repoRoot);
 }
 
 /** Resolve one commit-ish ref to the exact commit object used for later blob reads. */

src/core/jj.ts

@@ -1,5 +1,6 @@
 import { HunkUserError } from "./errors";
 import type { VcsCommandInput, ShowCommandInput } from "./types";
+import { normalizeWindowsPath } from "../lib/windowsPath";
 
 export type JjBackedInput = VcsCommandInput | ShowCommandInput;
 
@@ -182,9 +183,10 @@ export function resolveJjRepoRoot(
   input: JjBackedInput,
   options: Omit<RunJjTextOptions, "input" | "args"> = {},
 ) {
-  return runJjText({
+  const repoRoot = runJjText({
     input,
     args: ["root"],
     ...options,
   }).trim();
+  return normalizeWindowsPath(repoRoot);
 }

src/core/sl.ts

@@ -2,6 +2,7 @@ import fs from "node:fs";
 import { join } from "node:path";
 import { HunkUserError } from "./errors";
 import type { VcsCommandInput, ShowCommandInput } from "./types";
+import { normalizeWindowsPath } from "../lib/windowsPath";
 
 export type SlBackedInput = VcsCommandInput | ShowCommandInput;
 
@@ -265,9 +266,10 @@ export function resolveSlRepoRoot(
   input: SlBackedInput,
   options: Omit<RunSlTextOptions, "input" | "args"> = {},
 ) {
-  return runSlText({
+  const repoRoot = runSlText({
     input,
     args: ["root"],
     ...options,
   }).trim();
+  return normalizeWindowsPath(repoRoot);
 }

src/lib/windowsPath.test.ts

@@ -0,0 +1,13 @@
+import { describe, expect, test } from "bun:test";
+import { normalizeWindowsPath } from "./windowsPath";
+
+describe("normalizeWindowsPath", () => {
+  test("normalizes Unix-style Windows paths for native subprocess cwd", () => {
+    expect(normalizeWindowsPath("/cygdrive/c/work/repo", "win32")).toBe("C:\\work\\repo");
+    expect(normalizeWindowsPath("/c/work/repo", "win32")).toBe("C:\\work\\repo");
+    expect(normalizeWindowsPath("/mnt/c/work/repo", "win32")).toBe("C:\\work\\repo");
+    expect(normalizeWindowsPath("/c:/work/repo", "win32")).toBe("C:\\work\\repo");
+    expect(normalizeWindowsPath("/home/project", "win32")).toBe("/home/project");
+    expect(normalizeWindowsPath("/cygdrive/c/work/repo", "linux")).toBe("/cygdrive/c/work/repo");
+  });
+});

src/lib/windowsPath.ts

@@ -0,0 +1,18 @@
+/** Convert Unix-style Windows paths to native paths usable as Bun cwd. */
+export function normalizeWindowsPath(path: string, platform = process.platform) {
+  if (platform !== "win32") {
+    return path;
+  }
+
+  const normalized = path
+    // Some Windows tools can report slash-prefixed drive paths as `/C:/...`.
+    .replace(/^\/([a-zA-Z]):(?:[\\/]|$)/, (_, drive) => `${drive.toUpperCase()}:/`)
+    // Git Bash/MSYS2 commonly reports drive paths as `/c/...`.
+    .replace(/^\/([a-zA-Z])(?:[\\/]|$)/, (_, drive) => `${drive.toUpperCase()}:/`)
+    // Cygwin commonly reports drive paths as `/cygdrive/c/...`.
+    .replace(/^\/cygdrive\/([a-zA-Z])(?:[\\/]|$)/, (_, drive) => `${drive.toUpperCase()}:/`)
+    // WSL-style paths are commonly reported as `/mnt/c/...`.
+    .replace(/^\/mnt\/([a-zA-Z])(?:[\\/]|$)/, (_, drive) => `${drive.toUpperCase()}:/`);
+
+  return normalized === path ? path : normalized.replaceAll("/", "\\");
+}