start_batch_changes() doesn't avoid invoking the clipboard
once-per-line, because the loop is actually in ex_echo(), which calls
redir_write() for each message. But we've already entered
start_batch_changes() by then, so that was never the problem.
redir_write at /home/vagrant/old.neovim/build/../src/nvim/message.c:2523
msg_puts_attr_len at /home/vagrant/old.neovim/build/../src/nvim/message.c:1600
msg_outtrans_len_attr at /home/vagrant/old.neovim/build/../src/nvim/message.c:1221
ex_echo at /home/vagrant/old.neovim/build/../src/nvim/eval.c:19433
do_one_cmd at /home/vagrant/old.neovim/build/../src/nvim/ex_docmd.c:2242
Trying to defer _explicit_ clipboard updates is difficult.
:redir @+ | silent echo system('cat foo') | redir END
is essentially equivalent to:
for l in readfile('foo')
let @+ .= l
endfor
We cannot make judgements about when to ignore a script's bad decisions.
start_batch_changes() only works around the case of clipboard=unnamed,
i.e. _implicit_ clipboard updates (`:g/foo/d`). Not explicit
assignment.
