patch 8.0.0716: not easy to start Vim cleanly
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".
diff --git a/src/option.h b/src/option.h
index c74a89b..7394c7f 100644
--- a/src/option.h
+++ b/src/option.h
@@ -920,6 +920,7 @@
#endif
#ifdef FEAT_VIMINFO
EXTERN char_u *p_viminfo; /* 'viminfo' */
+EXTERN char_u *p_viminfofile; /* 'viminfofile' */
#endif
#ifdef FEAT_SESSION
EXTERN char_u *p_vdir; /* 'viewdir' */