commit: move check for incompatible args earlier

I think it makes sense to check the command line arguments as early as possible,
so we don't have to wait for a repo lock to tell the user that they passed
invalid arguments.

mercurial/commands.py

@@ -2082,6 +2082,7 b' def commit(ui, repo, *pats, **opts):'
 
           hg commit --amend --date now
     """
+    cmdutil.check_incompatible_arguments(opts, 'subrepos', ['amend'])
     with repo.wlock(), repo.lock():
         return _docommit(ui, repo, *pats, **opts)
 
@@ -2097,7 +2098,6 b' def _docommit(ui, repo, *pats, **opts):'
         return 1 if ret == 0 else ret
 
     if opts.get('subrepos'):
-        cmdutil.check_incompatible_arguments(opts, 'subrepos', ['amend'])
         # Let --subrepos on the command line override config setting.
         ui.setconfig(b'ui', b'commitsubrepos', True, b'commit')