file: Add windows support for non-overwrite

Cargo.toml

@@ -24,7 +24,7 @@ rayon = "1.10.0"
 libc = "0.2.161"
 
 [target.'cfg(target_family = "windows")'.dependencies]
-winapi = { version = "0.3.9", features = ["winerror"] }
+winapi = { version = "0.3.9", features = ["errhandlingapi", "winbase", "winerror"] }
 
 [dev-dependencies]
 assert_cmd = "2.0.16"

src/file.rs

@@ -38,7 +38,7 @@ fn rename(from: &Path, to: &Path, overwrite: bool) -> io::Result<()> {
     }
 }
 
-#[cfg(not(target_os = "linux"))]
+#[cfg(not(any(target_os = "linux", target_family = "windows")))]
 fn rename(from: &Path, to: &Path, overwrite: bool) -> io::Result<()> {
     use crate::util::die;
     if !overwrite {
@@ -47,6 +47,39 @@ fn rename(from: &Path, to: &Path, overwrite: bool) -> io::Result<()> {
     fs::rename(from, to)
 }
 
+#[cfg(target_family = "windows")]
+fn rename(from: &Path, to: &Path, overwrite: bool) -> io::Result<()> {
+    use std::os::windows::ffi::OsStrExt;
+    use winapi::um::errhandlingapi::GetLastError;
+    use winapi::um::winbase::{MoveFileExW, MOVEFILE_COPY_ALLOWED, MOVEFILE_REPLACE_EXISTING};
+
+    let from_wide: Vec<u16> = from
+        .as_os_str()
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect();
+    let to_wide: Vec<u16> = to
+        .as_os_str()
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect();
+
+    let mut flags = MOVEFILE_COPY_ALLOWED;
+    if overwrite {
+        flags |= MOVEFILE_REPLACE_EXISTING;
+    }
+
+    // SAFETY: Simple FFI
+    let ret = unsafe { MoveFileExW(from_wide.as_ptr(), to_wide.as_ptr(), flags) };
+
+    if ret == 0 {
+        let err = unsafe { GetLastError() };
+        Err(io::Error::from_raw_os_error(err as i32))
+    } else {
+        Ok(())
+    }
+}
+
 pub fn copy_creating_dirs(from: &Path, to_raw: impl Into<PathBuf>, overwrite: bool) -> Result<()> {
     let to = to_raw.into();
     let to_parent = to.parent().context("refusing to copy to filesystem root")?;

tests/integration_tests.rs

@@ -1,6 +1,6 @@
 use anyhow::Result;
 
-#[cfg(target_os = "linux")] // Others must use --overwrite
+#[cfg(any(target_os = "linux", target_family = "windows"))] // Others must use --overwrite
 #[test]
 fn test_rename_no_overwrite() -> Result<()> {
     // Set up test environment