fix: rename test modules to avoid case-insensitive path collisions

Cloning the repo on case-insensitive filesystems (e.g. Windows, macOS)
produces git warnings because the following directories collide:

  tests/{source,target}/reorder_modules/ABCD vs abcd
  tests/{source,target}/reorder_modules/ZYXW vs zyxw
  tests/{source,target}/reorder_modules_2027/ABCD vs abcd
  tests/{source,target}/reorder_modules_2027/ZYXW vs zyxw

These were added in 2d049af (#6368) to test
case-sensitive module sorting across style editions. The collision on
case-insensitive filesystems was not considered.

Rename the lowercase variants (abcd -> abcde, zyxw -> zyxwv) to
eliminate collisions while preserving the test intent.

Also add a unit test (no_case_insensitive_path_collisions) to prevent
future collisions, as suggested by @ytmimi.

src/test/mod.rs

@@ -166,6 +166,58 @@ fn verify_config_test_names() {
     }
 }
 
+// Collects all file and directory paths under `root` (relative to `root`).
+fn collect_paths(root: &Path) -> Vec<PathBuf> {
+    let mut paths = Vec::new();
+    let mut stack = vec![root.to_path_buf()];
+    while let Some(dir) = stack.pop() {
+        for entry in fs::read_dir(&dir).expect(&format!("couldn't read {}", dir.display())) {
+            let entry = entry.expect("couldn't get DirEntry");
+            let path = entry.path();
+            paths.push(path.strip_prefix(root).unwrap().to_path_buf());
+            if path.is_dir() {
+                stack.push(path);
+            }
+        }
+    }
+    paths
+}
+
+#[test]
+fn no_case_insensitive_path_collisions() {
+    // Ensure no two paths in test directories differ only by case,
+    // which causes warnings when cloning on case-insensitive filesystems
+    // (e.g. Windows, macOS).
+    let test_dirs = [Path::new("tests/source"), Path::new("tests/target")];
+    let mut collisions = Vec::new();
+
+    for root in &test_dirs {
+        let mut seen: HashMap<String, PathBuf> = HashMap::new();
+        for path in collect_paths(root) {
+            let key = path.to_string_lossy().to_lowercase();
+            if let Some(existing) = seen.get(&key) {
+                if *existing != path {
+                    collisions.push(format!(
+                        "{}/{} collides with {}/{}",
+                        root.display(),
+                        existing.display(),
+                        root.display(),
+                        path.display(),
+                    ));
+                }
+            } else {
+                seen.insert(key, path);
+            }
+        }
+    }
+
+    assert!(
+        collisions.is_empty(),
+        "Case-insensitive path collisions found (these cause warnings on Windows/macOS):\n  {}",
+        collisions.join("\n  ")
+    );
+}
+
 // This writes to the terminal using the same approach (via `term::stdout` or
 // `println!`) that is used by `rustfmt::rustfmt_diff::print_diff`. Writing
 // using only one or the other will cause the output order to differ when

tests/source/reorder_modules/disabled_style_edition_2024.rs

@@ -5,7 +5,7 @@ mod x86;
 mod v0s;
 mod v001;
 mod x87;
-mod zyxw;
+mod zyxwv;
 mod A2;
 mod ZYXW;
 mod w5s009t;
@@ -36,7 +36,7 @@ mod _abcd;
 mod ABCD;
 mod Z_YXW;
 mod u64;
-mod abcd;
+mod abcde;
 mod ZYXW_;
 mod u16;
 mod uz;

tests/source/reorder_modules/enabled_style_edition_2015.rs

@@ -5,7 +5,7 @@ mod x86;
 mod v0s;
 mod v001;
 mod x87;
-mod zyxw;
+mod zyxwv;
 mod A2;
 mod ZYXW;
 mod w5s009t;
@@ -36,7 +36,7 @@ mod _abcd;
 mod ABCD;
 mod Z_YXW;
 mod u64;
-mod abcd;
+mod abcde;
 mod ZYXW_;
 mod u16;
 mod uz;

tests/source/reorder_modules/enabled_style_edition_2024.rs

@@ -5,7 +5,7 @@ mod x86;
 mod v0s;
 mod v001;
 mod x87;
-mod zyxw;
+mod zyxwv;
 mod A2;
 mod ZYXW;
 mod w5s009t;
@@ -36,7 +36,7 @@ mod _abcd;
 mod ABCD;
 mod Z_YXW;
 mod u64;
-mod abcd;
+mod abcde;
 mod ZYXW_;
 mod u16;
 mod uz;

tests/source/reorder_modules_2027/disabled_style_edition_2027.rs

@@ -5,7 +5,7 @@ mod x86;
 mod v0s;
 mod v001;
 mod x87;
-mod zyxw;
+mod zyxwv;
 mod A2;
 mod ZYXW;
 mod w5s009t;
@@ -36,7 +36,7 @@ mod _abcd;
 mod ABCD;
 mod Z_YXW;
 mod u64;
-mod abcd;
+mod abcde;
 mod ZYXW_;
 mod u16;
 mod uz;

tests/source/reorder_modules_2027/enabled_style_edition_2027.rs

@@ -5,7 +5,7 @@ mod x86;
 mod v0s;
 mod v001;
 mod x87;
-mod zyxw;
+mod zyxwv;
 mod A2;
 mod ZYXW;
 mod w5s009t;
@@ -36,7 +36,7 @@ mod _abcd;
 mod ABCD;
 mod Z_YXW;
 mod u64;
-mod abcd;
+mod abcde;
 mod ZYXW_;
 mod u16;
 mod uz;

tests/target/reorder_modules/abcde/mod.rs

@@ -0,0 +1 @@
+

tests/target/reorder_modules/disabled_style_edition_2024.rs

@@ -5,7 +5,7 @@ mod x86;
 mod v0s;
 mod v001;
 mod x87;
-mod zyxw;
+mod zyxwv;
 mod A2;
 mod ZYXW;
 mod w5s009t;
@@ -36,7 +36,7 @@ mod _abcd;
 mod ABCD;
 mod Z_YXW;
 mod u64;
-mod abcd;
+mod abcde;
 mod ZYXW_;
 mod u16;
 mod uz;

tests/target/reorder_modules/enabled_style_edition_2015.rs

@@ -11,7 +11,7 @@ mod Z_YXW;
 mod _ZYXW;
 mod _abcd;
 mod a1;
-mod abcd;
+mod abcde;
 mod u128;
 mod u16;
 mod u256;
@@ -44,4 +44,4 @@ mod x86_128;
 mod x86_32;
 mod x86_64;
 mod x87;
-mod zyxw;
+mod zyxwv;

tests/target/reorder_modules/enabled_style_edition_2024.rs

@@ -11,7 +11,7 @@ mod Z_YXW;
 mod _ZYXW;
 mod _abcd;
 mod a1;
-mod abcd;
+mod abcde;
 mod u128;
 mod u16;
 mod u256;
@@ -44,4 +44,4 @@ mod x86_128;
 mod x86_32;
 mod x86_64;
 mod x87;
-mod zyxw;
+mod zyxwv;

tests/target/reorder_modules/zyxwv/mod.rs

@@ -0,0 +1 @@
+

tests/target/reorder_modules_2027/abcde/mod.rs

@@ -0,0 +1 @@
+

tests/target/reorder_modules_2027/disabled_style_edition_2027.rs

@@ -5,7 +5,7 @@ mod x86;
 mod v0s;
 mod v001;
 mod x87;
-mod zyxw;
+mod zyxwv;
 mod A2;
 mod ZYXW;
 mod w5s009t;
@@ -36,7 +36,7 @@ mod _abcd;
 mod ABCD;
 mod Z_YXW;
 mod u64;
-mod abcd;
+mod abcde;
 mod ZYXW_;
 mod u16;
 mod uz;

tests/target/reorder_modules_2027/enabled_style_edition_2027.rs

@@ -11,7 +11,7 @@ mod ZY_XW;
 mod ZYXW;
 mod ZYXW_;
 mod a1;
-mod abcd;
+mod abcde;
 mod u_zzz;
 mod u8;
 mod u16;
@@ -44,4 +44,4 @@ mod x86_32;
 mod x86_64;
 mod x86_128;
 mod x87;
-mod zyxw;
+mod zyxwv;

tests/target/reorder_modules_2027/zyxwv/mod.rs

@@ -0,0 +1 @@
+