feat: hide .jj directory on Windows

Cargo.toml

@@ -117,7 +117,7 @@ version_check = "0.9.5"
 watchman_client = { version = "0.9.0" }
 whoami = "1.6.0"
 winreg = "0.52"
-
+winapi= {version = "0.3.9", features = ["winuser"] }
 # put all inter-workspace libraries, i.e. those that use 'path = ...' here in
 # their own (alphabetically sorted) block
 

lib/Cargo.toml

@@ -79,6 +79,7 @@ rustix = { workspace = true }
 
 [target.'cfg(windows)'.dependencies]
 winreg = { workspace = true }
+winapi = { workspace = true }
 
 [dev-dependencies]
 assert_matches = { workspace = true }

lib/src/lib.rs

@@ -16,7 +16,7 @@
 
 #![warn(missing_docs)]
 #![deny(unused_must_use)]
-#![forbid(unsafe_code)]
+#![deny(unsafe_code)]
 
 // Needed so that proc macros can be used inside jj_lib and by external crates
 // that depend on it.

lib/src/workspace.rs

@@ -15,6 +15,8 @@
 #![allow(missing_docs)]
 
 use std::collections::HashMap;
+#[cfg(windows)]
+use std::ffi::CString;
 use std::fs;
 use std::fs::File;
 use std::io;
@@ -24,6 +26,10 @@ use std::path::PathBuf;
 use std::sync::Arc;
 
 use thiserror::Error;
+#[cfg(windows)]
+use winapi::um::fileapi::SetFileAttributesA;
+#[cfg(windows)]
+use winapi::um::winnt::FILE_ATTRIBUTE_HIDDEN;
 
 use crate::backend::BackendInitError;
 use crate::backend::MergedTreeId;
@@ -119,7 +125,17 @@ pub struct Workspace {
 fn create_jj_dir(workspace_root: &Path) -> Result<PathBuf, WorkspaceInitError> {
     let jj_dir = workspace_root.join(".jj");
     match std::fs::create_dir(&jj_dir).context(&jj_dir) {
-        Ok(()) => Ok(jj_dir),
+        Ok(()) => {
+            #[cfg(windows)]
+            #[allow(unsafe_code)]
+            {
+                let jj_dir = CString::new(jj_dir.to_str().unwrap()).unwrap();
+                unsafe {
+                    SetFileAttributesA(jj_dir.as_ptr(), FILE_ATTRIBUTE_HIDDEN);
+                };
+            }
+            Ok(jj_dir)
+        }
         Err(ref e) if e.error.kind() == io::ErrorKind::AlreadyExists => {
             Err(WorkspaceInitError::DestinationExists(jj_dir))
         }

lib/tests/test_init.rs

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#[cfg(windows)]
+use std::ffi::CString;
 use std::path::Path;
 use std::path::PathBuf;
 
@@ -26,6 +28,10 @@ use testutils::git;
 use testutils::write_random_commit;
 use testutils::TestRepoBackend;
 use testutils::TestWorkspace;
+#[cfg(windows)]
+use winapi::um::fileapi::GetFileAttributesA;
+#[cfg(windows)]
+use winapi::um::winnt::FILE_ATTRIBUTE_HIDDEN;
 
 fn canonicalize(input: &Path) -> (PathBuf, PathBuf) {
     let uncanonical = input.join("..").join(input.file_name().unwrap());
@@ -51,6 +57,20 @@ fn test_init_local() {
     write_random_commit(tx.repo_mut());
 }
 
+#[test]
+#[cfg(windows)]
+fn test_init_hidden() {
+    let settings = testutils::user_settings();
+    let temp_dir = testutils::new_temp_dir();
+    let (canonical, uncanonical) = canonicalize(temp_dir.path());
+    Workspace::init_internal_git(&settings, &uncanonical).unwrap();
+
+    let dot_jj_path = CString::new(canonical.join(".jj").to_str().unwrap()).unwrap();
+    let dot_jj_folder_attributes = unsafe { GetFileAttributesA(dot_jj_path.as_ptr()) };
+
+    assert_ne!(dot_jj_folder_attributes & FILE_ATTRIBUTE_HIDDEN, 0);
+}
+
 #[test]
 fn test_init_internal_git() {
     let settings = testutils::user_settings();