fix: suppress "no more pattern" messages

If you start at the first occurrence of a search word in a buffer then
get to the end and the substitution command repeats from the top there
is no more occurrence of the word and so throws an error.

Let's try to suppress that error by only doing the second substitution
from the fist line to the line above the cursor position if that search
word exists.

Again, this is a lot of code for such a nicety of not jumping to the top
of a file during a search/replace. Time will tell if it's worth it.

There remain issues:

- the words above the cursor don't highligh with the Substitute highlight
  group.
- they do highlight after you press enter to start substitution, which is
  also odd
- the message after the first substitution is correct, e.g. replaced 3
  words on 3 lines, but the second one doesn't occur and makes the first
  one wrong since you just replaced more words!

plugin/scalpel.lua

@@ -2,18 +2,33 @@
 -- scalpel.lua
 --
 
+local function word_exists_above_cursor(word)
+  local current_line = vim.api.nvim_win_get_cursor(0)[1]
+  for i = current_line - 1, 1, -1 do
+    local line = vim.api.nvim_buf_get_lines(0, i - 1, i, false)[1]
+    if string.find(line, word) then
+      return true
+    end
+  end
+  return false
+end
+
 local function substitute_current_word()
   local word = vim.fn.expand('<cword>')
-  local pattern = ':,$s/\\v(' .. word .. ")//gc|:undojoin|1,''-&&"
+  local substituation_command_down = ':,$s/\\v(' .. word .. ')//gc'
+  local repeat_from_top_to_current_line = "|1,''-&&"
+  local cursor_move_to_replace_pattern
+
+  if word_exists_above_cursor(word) then
+    substituation_command_down = substituation_command_down .. repeat_from_top_to_current_line
+    cursor_move_to_replace_pattern = '<Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left>'
+  else
+    cursor_move_to_replace_pattern = '<Left><Left><Left>'
+  end
 
-  local cursor_move = vim.api.nvim_replace_termcodes(
-    '<Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left><Left>',
-    true,
-    false,
-    true
-  )
+  local cursor_move = vim.api.nvim_replace_termcodes(cursor_move_to_replace_pattern, true, false, true)
 
-  vim.api.nvim_feedkeys(pattern .. cursor_move, 'n', true)
+  vim.api.nvim_feedkeys(substituation_command_down .. cursor_move, 'n', true)
 end
 
 vim.keymap.set('n', '<leader>e', substitute_current_word, { desc = 'Substite current word in file' })