mergestate: use `update_file` to handle for `ACTION_EXEC`

This is the newer, more semantic API.

Differential Revision: https://phab.mercurial-scm.org/D11169

mercurial/mergestate.py

@@ -776,7 +776,9 b' def recordupdates(repo, actions, branchm'
 
     # exec change
     for f, args, msg in actions.get(ACTION_EXEC, []):
-        repo.dirstate.normallookup(f)
+        repo.dirstate.update_file(
+            f, p1_tracked=True, wc_tracked=True, possibly_dirty=True
+        )
 
     # keep
     for f, args, msg in actions.get(ACTION_KEEP, []):