Address performance regression: When loading very very large diffs,

appending to the output buffer would perform way way way too much string
allocations/rehashing.

To address this, we can stop appending output to this buffer after 300
lines. It may be worth persuing not appending anything to this buffer at
all unless it's a PTY process, but that can be looked into later.

Author: CKolkey

lua/neogit/buffers/process/init.lua

@@ -3,6 +3,8 @@ local config = require("neogit.config")
 local status_maps = require("neogit.config").get_reversed_status_maps()
 
 ---@class ProcessBuffer
+---@field lines integer
+---@field truncated boolean
 ---@field buffer Buffer
 ---@field open fun(self)
 ---@field hide fun(self)
@@ -24,6 +26,8 @@ function M:new(process)
     content = string.format("> %s\r\n", table.concat(process.cmd, " ")),
     process = process,
     buffer = nil,
+    lines = 0,
+    truncated = false,
   }
 
   setmetatable(instance, self)
@@ -67,6 +71,20 @@ function M:refresh()
 end
 
 function M:append(data)
+  self.lines = self.lines + 1
+  if self.lines > 300 then
+    if not self.truncated then
+      self.content = table.concat({ self.content, "\r\n[Output too long - Truncated]" }, "\r\n")
+      self.truncated = true
+
+      if self:is_visible() then
+        self:refresh()
+      end
+    end
+
+    return
+  end
+
   self.content = table.concat({ self.content, data }, "\r\n")
 
   if self:is_visible() then

lua/neogit/process.lua

@@ -249,15 +249,13 @@ function Process:spawn(cb)
 
   local stdout_on_line = function(line)
     insert(res.stdout, line)
-    insert(res.output, line)
     self.buffer:append(line)
   end
 
   local stderr_on_partial = function() end
 
   local stderr_on_line = function(line)
     insert(res.stderr, line)
-    insert(res.output, line)
     self.buffer:append(line)
   end