fix(terminal): spawn in effective CWD #41211

Problem:
`:terminal` does not respect the invocation-time CWD.
This wasn't noticeable with `:lcd` because the window-local CWD gets
applied to the new terminal buffer. But it is noticeable with `:bcd`.

Solution:
Specify `cwd` in the job spec.

runtime/lua/vim/_core/ex_cmd.lua

@@ -248,17 +248,20 @@ function M.ex_terminal(eap, shell_argv)
     or smods.horizontal
     or smods.vertical
 
+  -- Use the invocation-time CWD, before creating a new buffer.
+  local opts = { term = true, cwd = vim.fn.getcwd() }
+
   if has_mods then
     vim.cmd.new { mods = smods }
   else
     vim.cmd.enew { bang = eap.bang }
   end
 
-  if shell_argv then -- No `cmd`, run 'shell'.
-    vim.fn.jobstart(shell_argv, { term = true })
-  else -- Run [cmd] in 'shell'.
-    vim.fn.jobstart(eap.args, { term = true })
-  end
+  vim.fn.jobstart(
+    shell_argv and shell_argv -- No `cmd`, run 'shell'.
+      or eap.args, -- Run [cmd] in 'shell'.
+    opts
+  )
 end
 
 function M.ex_uptime()

test/functional/terminal/ex_terminal_spec.lua

@@ -13,7 +13,6 @@ local fn = n.fn
 local api = n.api
 local exec_lua = n.exec_lua
 local retry = t.retry
-local pcall_err = t.pcall_err
 local ok = t.ok
 local command = n.command
 local skip = t.skip
@@ -268,6 +267,16 @@ local function test_terminal_with_fake_shell(backslash)
     ]])
   end)
 
+  it('spawns in CWD effective at time of invocation', function()
+    command('terminal')
+    local dir = fn.bufname():match('^term://(.-)//')
+    command('bcd ..') -- :terminal should use this CWD.
+    command('terminal')
+    local parent = fn.bufname():match('^term://(.-)//')
+    neq(dir, parent)
+    eq(fn.fnamemodify(dir, ':h'), parent)
+  end)
+
   it('allows quotes and slashes', function()
     command([[terminal echo 'hello' \ "world"]])
     screen:expect([[
@@ -360,7 +369,7 @@ local function test_terminal_with_fake_shell(backslash)
   end)
 end
 
-describe(':terminal (with fake shell)', function()
+describe(':terminal (fake shell)', function()
   test_terminal_with_fake_shell(false)
   if is_os('win') then
     describe("when 'shell' uses backslashes", function()