fix(blame): do not run concurrent processes

Fixes #877

lua/gitsigns/current_line_blame.lua

@@ -7,6 +7,7 @@ local uv = vim.loop
 local api = vim.api
 
 local current_buf = api.nvim_get_current_buf
+local throttle_by_id = require('gitsigns.debounce').throttle_by_id
 
 local namespace = api.nvim_create_namespace('gitsigns_blame')
 
@@ -183,9 +184,9 @@ local function get_lnum()
   return api.nvim_win_get_cursor(0)[1]
 end
 
--- Update function, must be called in async context
-local function update0()
-  local bufnr = current_buf()
+--- Update function, must be called in async context
+--- @param bufnr integer
+local function update0(bufnr)
   local lnum = get_lnum()
 
   local old_lnum = get_extmark(bufnr)
@@ -231,7 +232,7 @@ local function update0()
   if bufnr == current_buf() and lnum ~= lnum1 then
     -- Cursor has moved during events; abort and tr-trigger another update
     -- since it's likely blame jobs where skipped
-    update0()
+    update0(bufnr)
     return
   end
 
@@ -242,7 +243,7 @@ local function update0()
   end
 end
 
-local update = async.void(update0)
+local update = async.void(throttle_by_id(update0))
 
 function M.setup()
   local group = api.nvim_create_augroup('gitsigns_blame', {})
@@ -254,7 +255,9 @@ function M.setup()
   if config.current_line_blame then
     api.nvim_create_autocmd({ 'FocusGained', 'BufEnter', 'CursorMoved', 'CursorMovedI' }, {
       group = group,
-      callback = update,
+      callback = function(args)
+        update(args.buf)
+      end
     })
 
     api.nvim_create_autocmd({ 'InsertEnter', 'FocusLost', 'BufLeave' }, {
@@ -266,7 +269,9 @@ function M.setup()
 
     -- Call via vim.schedule to avoid the debounce timer killing the async
     -- coroutine
-    vim.schedule(update)
+    vim.schedule(function()
+      update(api.nvim_get_current_buf())
+    end)
   end
 end