fix: ignore .gitignore files that are directories

This happens in real-life, and Git itself doesn't budge.

gix-glob/src/search/pattern.rs

@@ -48,16 +48,29 @@ fn read_in_full_ignore_missing(path: &Path, follow_symlinks: bool, buf: &mut Vec
     };
     Ok(match file {
         Ok(mut file) => {
-            file.read_to_end(buf)?;
-            true
+            if let Err(err) = file.read_to_end(buf) {
+                if io_err_is_dir(&err) {
+                    false
+                } else {
+                    return Err(err);
+                }
+            } else {
+                true
+            }
         }
-        Err(err) if err.kind() == std::io::ErrorKind::NotFound ||
-            // TODO: use the enum variant NotADirectory for this once stabilized
-            err.raw_os_error() == Some(20) /* Not a directory */ => false,
+        Err(err) if err.kind() == std::io::ErrorKind::NotFound || io_err_is_dir(&err) => false,
         Err(err) => return Err(err),
     })
 }
 
+fn io_err_is_dir(err: &std::io::Error) -> bool {
+    // TODO: use the enum variant NotADirectory for this once stabilized
+    let raw = err.raw_os_error();
+    raw == Some(if cfg!(windows) { 5 } else { 21 }) /* Not a directory */
+        /* Also that, but under different circumstances */
+        || raw == Some(20)
+}
+
 /// Instantiation
 impl<T> List<T>
 where

gix-glob/tests/search/pattern.rs

@@ -85,7 +85,7 @@ mod list {
     }
 
     #[test]
-    fn from_file() {
+    fn from_file_that_does_not_exist() {
         let mut buf = Vec::new();
         for path in [
             Path::new(".").join("non-existing-dir").join("pattern-file"),
@@ -95,4 +95,16 @@ mod list {
             assert!(list.is_none(), "the file does not exist");
         }
     }
+
+    #[test]
+    fn from_file_that_is_a_directory() -> gix_testtools::Result<()> {
+        let tmp = gix_testtools::tempfile::TempDir::new()?;
+        let dir_path = tmp.path().join(".gitignore");
+        std::fs::create_dir(&dir_path)?;
+        let mut buf = Vec::new();
+        let list = List::<Dummy>::from_file(dir_path, None, false, &mut buf).expect("no io error");
+        assert!(list.is_none(), "directories are ignored just like Git does it");
+
+        Ok(())
+    }
 }