vim-patch:8.0.0716: "--clean", 'shadafile' #9907

Nvim notes:
- Nvim does not support "-u DEFAULTS", that change is omitted.
- Also add 'shadafile' as an alias to 'viminfofile'.
- Deprecate 'viminfofile'.

Problem:    Not easy to start Vim cleanly without changing the viminfo file.
            Not possible to know whether the -i command line flag was used.
Solution:   Add the --clean command line argument.  Add the 'viminfofile'
            option.  Add "-u DEFAULTS".
c4da113ef9

src/nvim/options.lua

@@ -2014,6 +2014,15 @@ return {
       varname='p_shada',
       defaults={if_true={vi="", vim="!,'100,<50,s10,h"}}
     },
+    {
+      full_name='shadafile', abbreviation='sdf',
+      type='string', list='onecomma', scope={'global'},
+      deny_duplicates=true,
+      vi_def=true,
+      secure=true,
+      varname='p_shadafile',
+      defaults={if_true={vi=""}}
+    },
     {
       full_name='shell', abbreviation='sh',
       type='string', scope={'global'},
@@ -2632,6 +2641,15 @@ return {
       varname='p_shada',
       defaults={if_true={vi="", vim="!,'100,<50,s10,h"}}
     },
+    {
+      full_name='viminfofile', abbreviation='vif',
+      type='string', list='onecomma', scope={'global'},
+      deny_duplicates=true,
+      vi_def=true,
+      secure=true,
+      varname='p_shadafile',
+      defaults={if_true={vi=""}}
+    },
     {
       full_name='virtualedit', abbreviation='ve',
       type='string', list='onecomma', scope={'global'},