GH-115060: Speed up pathlib.Path.glob() by not scanning literal parts (#117732)

Don't bother calling `os.scandir()` to scan for literal pattern segments,
like `foo` in `foo/*.py`. Instead, append the segment(s) as-is and call
through to the next selector with `exists=False`, which signals that the
path might not exist. Subsequent selectors will call `os.scandir()` or
`os.lstat()` to filter out missing paths as needed.

Lib/glob.py

@@ -331,9 +331,10 @@ class _Globber:
     """Class providing shell-style pattern matching and globbing.
     """
 
-    def __init__(self,  sep, case_sensitive, recursive=False):
+    def __init__(self, sep, case_sensitive, case_pedantic=False, recursive=False):
         self.sep = sep
         self.case_sensitive = case_sensitive
+        self.case_pedantic = case_pedantic
         self.recursive = recursive
 
     # Low-level methods
@@ -373,6 +374,8 @@ class _Globber:
             selector = self.recursive_selector
         elif part in _special_parts:
             selector = self.special_selector
+        elif not self.case_pedantic and magic_check.search(part) is None:
+            selector = self.literal_selector
         else:
             selector = self.wildcard_selector
         return selector(part, parts)
@@ -387,6 +390,23 @@ class _Globber:
             return select_next(path, exists)
         return select_special
 
+    def literal_selector(self, part, parts):
+        """Returns a function that selects a literal descendant of a path.
+        """
+
+        # Optimization: consume and join any subsequent literal parts here,
+        # rather than leaving them for the next selector. This reduces the
+        # number of string concatenation operations and calls to add_slash().
+        while parts and magic_check.search(parts[-1]) is None:
+            part += self.sep + parts.pop()
+
+        select_next = self.selector(parts)
+
+        def select_literal(path, exists=False):
+            path = self.concat_path(self.add_slash(path), part)
+            return select_next(path, exists=False)
+        return select_literal
+
     def wildcard_selector(self, part, parts):
         """Returns a function that selects direct children of a given path,
         filtering by pattern.