patch 8.2.2778: problem restoring 'packpath' in session

Problem:    Problem restoring 'packpath' in session.
Solution:   Let "skiprtp" also apply to 'packpath'.

runtime/doc/options.txt

@@ -6511,7 +6511,7 @@ A jump table for the options with a short description can be found at |Q_op|.
 			global values for local options)
 	   options	all options and mappings (also global values for local
 			options)
-	   skiprtp	exclude 'runtimepath' from the options
+	   skiprtp	exclude 'runtimepath' and 'packpath' from the options
 	   resize	size of the Vim window: 'lines' and 'columns'
 	   sesdir	the directory in which the session file is located
 			will become the current directory (useful with

src/option.c

@@ -4615,7 +4615,8 @@ makeset(FILE *fd, int opt_flags, int local_only)
 	    if ((opt_flags & OPT_GLOBAL) && optval_default(p, varp, p_cp))
 		continue;
 
-	    if ((opt_flags & OPT_SKIPRTP) && p->var == (char_u *)&p_rtp)
+	    if ((opt_flags & OPT_SKIPRTP) && (p->var == (char_u *)&p_rtp
+						 || p->var == (char_u *)&p_pp))
 		continue;
 
 	    round = 2;

src/testdir/test_mksession.vim

@@ -133,21 +133,25 @@ endfunc
 
 def Test_mksession_skiprtp()
   mksession! Xtest_mks.out
-  var found = 0
+  var found_rtp = 0
+  var found_pp = 0
   for line in readfile('Xtest_mks.out')
     if line =~ 'set runtimepath'
-      found = 1
-      break
+      found_rtp += 1
+    endif
+    if line =~ 'set packpath'
+      found_pp += 1
     endif
   endfor
-  assert_equal(1, found)
+  assert_equal(1, found_rtp)
+  assert_equal(1, found_pp)
   delete('Xtest_mks.out')
 
   set sessionoptions+=skiprtp
   mksession! Xtest_mks.out
-  found = 0
+  var found = 0
   for line in readfile('Xtest_mks.out')
-    if line =~ 'set runtimepath'
+    if line =~ 'set \(runtimepath\|packpath\)'
       found = 1
       break
     endif

src/version.c

@@ -750,6 +750,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    2778,
 /**/
     2777,
 /**/