Address code review feedback

- Use substr() instead of str_replace() for path manipulation to avoid edge cases
- Add comment explaining the use of 'test' as a probe filename
- Replace Bash-specific syntax with portable POSIX shell commands in tests
- Fix code style (trailing whitespace)

Co-authored-by: swissspidy <[email protected]>

Author: Copilot

features/distignore.feature

@@ -405,13 +405,13 @@ Feature: Generate a distribution archive of a project with .distignore
     When I run `mkdir -p foo/node_modules/package1 foo/node_modules/package2 foo/node_modules/package3`
     Then STDERR should be empty
 
-    When I run `for i in {1..50}; do touch foo/node_modules/package1/file$i.js; done`
+    When I run `sh -c 'i=1; while [ $i -le 50 ]; do touch foo/node_modules/package1/file$i.js; i=$((i+1)); done'`
     Then STDERR should be empty
 
-    When I run `for i in {1..50}; do touch foo/node_modules/package2/file$i.js; done`
+    When I run `sh -c 'i=1; while [ $i -le 50 ]; do touch foo/node_modules/package2/file$i.js; i=$((i+1)); done'`
     Then STDERR should be empty
 
-    When I run `for i in {1..50}; do touch foo/node_modules/package3/file$i.js; done`
+    When I run `sh -c 'i=1; while [ $i -le 50 ]; do touch foo/node_modules/package3/file$i.js; i=$((i+1)); done'`
     Then STDERR should be empty
 
     When I run `wp dist-archive foo`

src/Distignore_Filter_Iterator.php

@@ -69,7 +69,16 @@ public function hasChildren() {
 		}
 
 		// For directories, check if they should be ignored.
-		$relative_filepath = str_replace( $this->source_dir_path, '', $item->getPathname() );
+		$pathname           = $item->getPathname();
+		$source_path_length = strlen( $this->source_dir_path );
+
+		// Extract relative path by removing the source directory prefix.
+		if ( 0 === strpos( $pathname, $this->source_dir_path ) ) {
+			$relative_filepath = substr( $pathname, $source_path_length );
+		} else {
+			// Fallback if path doesn't start with source path (shouldn't happen).
+			$relative_filepath = $pathname;
+		}
 
 		try {
 			$is_ignored = $this->checker->isPathIgnored( $relative_filepath );
@@ -87,6 +96,8 @@ public function hasChildren() {
 				// This is a top-level ignored directory like "/node_modules" or "/.git".
 				// It's likely safe to skip descent as these are typically simple patterns.
 				// However, we still need to be conservative. Let's check if a child would be ignored.
+				// We use 'test' as a probe filename to check if children would be ignored.
+				// The actual name doesn't matter; we just need to verify the pattern applies to children.
 				$test_child = $relative_filepath . '/test';
 				try {
 					$child_ignored = $this->checker->isPathIgnored( $test_child );