refactor(sign): move legacy signs to extmarks

Problem:  The legacy signlist data structures and associated functions are
          redundant since the introduction of extmark signs.
Solution: Store signs defined through the legacy commands in a hashmap, placed
          signs in the extmark tree. Replace signlist associated functions.

Usage of the legacy sign commands should yield no change in behavior with the
exception of:
  - "orphaned signs" are now always removed when the line it is placed on is
    deleted. This used to depend on the value of 'signcolumn'.
  - It is no longer possible to place multiple signs with the same identifier
    in a single group on multiple lines. This will now move the sign instead.

Moreover, both signs placed through the legacy sign commands and through
|nvim_buf_set_extmark()|:
  - Will show up in both |sign-place| and |nvim_buf_get_extmarks()|.
  - Are displayed by increasing sign identifier, left to right.
    Extmark signs used to be ordered decreasingly as opposed to legacy signs.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/nvim/eval/buffer.c b/src/nvim/eval/buffer.c
index a26ba54ca3..616c1e06fc 100644
--- a/src/nvim/eval/buffer.c
+++ b/src/nvim/eval/buffer.c
@@ -504,7 +504,7 @@ static dict_T *get_buffer_info(buf_T *buf)
   }
   tv_dict_add_list(dict, S_LEN("windows"), windows);
 
-  if (buf->b_signlist != NULL) {
+  if (buf->b_signs) {
     // List of signs placed in this buffer
     tv_dict_add_list(dict, S_LEN("signs"), get_buffer_signs(buf));
   }