patch 8.2.0604: :startinsert in a terminal window used later

Problem:    :startinsert in a terminal window used later.
Solution:   Ignore :startinsert in a terminal window. (closes #5952)
diff --git a/src/testdir/test_terminal.vim b/src/testdir/test_terminal.vim
index 7b92774..549fdd1 100644
--- a/src/testdir/test_terminal.vim
+++ b/src/testdir/test_terminal.vim
@@ -2612,4 +2612,26 @@
   set hidden&
 endfunc
 
+func Test_term_and_startinsert()
+  CheckRunVimInTerminal
+  CheckUnix
+
+  let lines =<< trim EOL
+     put='some text'
+     term
+     startinsert
+  EOL
+  call writefile(lines, 'XTest_startinsert')
+  let buf = RunVimInTerminal('-S XTest_startinsert', {})
+
+  call term_sendkeys(buf, "exit\r")
+  call WaitForAssert({-> assert_equal("some text", term_getline(buf, 1))})
+  call term_sendkeys(buf, "0l")
+  call term_sendkeys(buf, "A<\<Esc>")
+  call WaitForAssert({-> assert_equal("some text<", term_getline(buf, 1))})
+
+  call StopVimInTerminal(buf)
+  call delete('XTest_startinsert')
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab