fix: correct rename on unix platforms caused by pathdiff#8 (#1587)

* fix: correct rename on unix platforms caused by pathdiff#8

* fix: ensure all calls to pathdiff

* fix: names

* fix: file path on windows

crates/tinymist-std/src/path.rs

@@ -1,6 +1,7 @@
 //! Path utilities.
 
-use std::path::{Component, Path};
+use std::borrow::Cow;
+use std::path::{Component, Path, PathBuf};
 
 pub use path_clean::PathClean;
 
@@ -48,6 +49,24 @@ pub fn unix_slash(root: &Path) -> String {
 /// Get the path cleaned as a platform-style string.
 pub use path_clean::clean;
 
+/// Construct a relative path from a provided base directory path to the
+/// provided path.
+pub fn diff(fr: &Path, to: &Path) -> Option<PathBuf> {
+    // Because of <https://github.com/Manishearth/pathdiff/issues/8>, we have to clean the path
+    // before diff.
+    fn clean_for_diff(p: &Path) -> Cow<'_, Path> {
+        if p.components()
+            .any(|c| matches!(c, Component::ParentDir | Component::CurDir))
+        {
+            Cow::Owned(p.clean())
+        } else {
+            Cow::Borrowed(p)
+        }
+    }
+
+    pathdiff::diff_paths(clean_for_diff(fr).as_ref(), clean_for_diff(to).as_ref())
+}
+
 #[cfg(test)]
 mod test {
     use std::path::{Path, PathBuf};