patch 8.0.0294: argument list is not stored correctly in a session file

Problem:    Argument list is not stored correctly in a session file.
            (lgpasquale)
Solution:   Use "$argadd" instead of "argadd". (closes #1434)

src/ex_docmd.c

@@ -11790,7 +11790,7 @@ ses_arglist(
 		    s = buf;
 		}
 	    }
-	    if (fputs("argadd ", fd) < 0
+	    if (fputs("$argadd ", fd) < 0
 		    || ses_put_fname(fd, s, flagp) == FAIL
 		    || put_eol(fd) == FAIL)
 	    {

src/testdir/test_mksession.vim

@@ -110,4 +110,16 @@ func Test_mksession_winheight()
   call delete('Xtest_mks.out')
 endfunc
 
+func Test_mksession_arglist()
+  argdel *
+  next file1 file2 file3 file4
+  mksession! Xtest_mks.out
+  source Xtest_mks.out
+  call assert_equal(['file1', 'file2', 'file3', 'file4'], argv())
+
+  call delete('Xtest_mks.out')
+  argdel *
+endfunc
+
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    294,
 /**/
     293,
 /**/