patch 8.1.0241: effect of ":tabmove N" is not clear

Problem:    Effect of ":tabmove N" is not clear.
Solution:   Add a test that shows the behavior. (Christian Brabandt,
            closes #3288)

Author: brammool

src/testdir/test_tabpage.vim

@@ -105,6 +105,19 @@ function Test_tabpage()
   call assert_equal(4, tabpagenr())
   7tabmove 5
   call assert_equal(5, tabpagenr())
+
+  " The following are a no-op
+  norm! 2gt
+  call assert_equal(2, tabpagenr())
+  tabmove 2
+  call assert_equal(2, tabpagenr())
+  2tabmove
+  call assert_equal(2, tabpagenr())
+  tabmove 1
+  call assert_equal(2, tabpagenr())
+  1tabmove
+  call assert_equal(2, tabpagenr())
+
   call assert_fails("99tabmove", 'E16:')
   call assert_fails("+99tabmove", 'E16:')
   call assert_fails("-99tabmove", 'E16:')

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    241,
 /**/
     240,
 /**/