vim-patch:8.1.2045: the option.c file is too big (#19854)

Problem:    The option.c file is too big.
Solution:   Split off the code dealing with strings. (Yegappan Lakshmanan,
            closes vim/vim#4937)
https://github.com/vim/vim/commit/dac1347b4d9c1a1aef6aa73fdea08a9d1077d6ea

Cherry-pick set_string_option_direct_in_win() from patch 8.1.1405.
Cherry-pick shift_line() comment change from patch 8.1.2096.
Move 'clipboard' default parsing to didset_string_options().
Reorder option flags to put Nvim-only flags at the end.

1 files changed, 2 insertions, 5 deletions

diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index c1fdbc1b9a..5485d528f7 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -34,6 +34,7 @@
 #include "nvim/move.h"
 #include "nvim/normal.h"
 #include "nvim/option.h"
+#include "nvim/optionstr.h"
 #include "nvim/os/os.h"
 #include "nvim/os/shell.h"
 #include "nvim/path.h"
@@ -1407,8 +1408,6 @@ void diff_win_options(win_T *wp, int addbuf)
     }
     wp->w_p_wrap = false;
   }
-  curwin = wp;  // -V519
-  curbuf = curwin->w_buffer;
 
   if (!wp->w_p_diff) {
     if (wp->w_p_diff_saved) {
@@ -1416,9 +1415,7 @@ void diff_win_options(win_T *wp, int addbuf)
     }
     wp->w_p_fdm_save = vim_strsave(wp->w_p_fdm);
   }
-  set_string_option_direct("fdm", -1, "diff", OPT_LOCAL | OPT_FREE, 0);
-  curwin = old_curwin;
-  curbuf = curwin->w_buffer;
+  set_string_option_direct_in_win(wp, "fdm", -1, "diff", OPT_LOCAL | OPT_FREE, 0);
 
   if (!wp->w_p_diff) {
     wp->w_p_fen_save = wp->w_p_fen;