hook: fix bug (reuse of variable) introduced in 872d49dd577a

For binary installs, the 'name' argument would be reused as a local variable,
destroying its original value. The patch fixes that, and also avoids copying
sys.path when it's not necessary.

mercurial/hook.py

@@ -27,13 +27,13 b' def _pythonhook(ui, repo, name, hname, f'
             raise util.Abort(_('%s hook is invalid ("%s" not in '
                                'a module)') % (hname, funcname))
         modname = funcname[:d]
-        oldpaths = sys.path[:]
+        oldpaths = sys.path
         if hasattr(sys, "frozen"):
             # binary installs require sys.path manipulation
-            path, name = os.path.split(modname)
-            if path and name:
-                sys.path.append(path)
-                modname = name
+            modpath, modfile = os.path.split(modname)
+            if modpath and modfile:
+                sys.path = sys.path[:] + [modpath]
+                modname = modfile
         try:
             obj = __import__(modname)
         except ImportError: