update: simplify slightly

update: simplify slightly

Differential Revision: https://phab.mercurial-scm.org/D8204

--- a/mercurial/commands.py	Sun Mar 01 21:16:45 2020 -0500
+++ b/mercurial/commands.py	Mon Mar 02 15:34:51 2020 -0500
@@ -7665,6 +7665,7 @@
 
     Returns 0 on success, 1 if there are unresolved files.
     """
+    cmdutil.check_at_most_one_arg(opts, b'clean', b'check', b'merge')
     rev = opts.get('rev')
     date = opts.get('date')
     clean = opts.get('clean')
@@ -7686,14 +7687,6 @@
     if date and rev is not None:
         raise error.Abort(_(b"you can't specify a revision and a date"))
 
-    if len([x for x in (clean, check, merge) if x]) > 1:
-        raise error.Abort(
-            _(
-                b"can only specify one of -C/--clean, -c/--check, "
-                b"or -m/--merge"
-            )
-        )
-
     updatecheck = None
     if check:
         updatecheck = b'abort'

--- a/tests/test-update-branches.t	Sun Mar 01 21:16:45 2020 -0500
+++ b/tests/test-update-branches.t	Mon Mar 02 15:34:51 2020 -0500
@@ -189,17 +189,17 @@
   parent=2
 
   $ revtest '-cC dirty linear'  dirty 1 2 -cC
-  abort: can only specify one of -C/--clean, -c/--check, or -m/--merge
+  abort: cannot specify both --clean and --check
   parent=1
   M foo
 
   $ revtest '-mc dirty linear'  dirty 1 2 -mc
-  abort: can only specify one of -C/--clean, -c/--check, or -m/--merge
+  abort: cannot specify both --check and --merge
   parent=1
   M foo
 
   $ revtest '-mC dirty linear'  dirty 1 2 -mC
-  abort: can only specify one of -C/--clean, -c/--check, or -m/--merge
+  abort: cannot specify both --clean and --merge
   parent=1
   M foo