Use the paste file in conemu for faster turnaround

[djha-skin]

This PR changes conemu to use the paste file instead of the windows clipboard. This can make it slightly faster if the clipboard is configured to use a subprocess like powershell.

Changes:

• The slime#common#write_paste_file now returns the name of the paste file to which it wrote, so that slime#resolve#config doesn't have to be called twice, once in the conemu#send and once in the write_paste_file method.
• The case where the paste file isn't written is checked.
• The paste file has the S flag set, which tells vim not to bother calling fsync() on the file, for faster write speeds. This makes sense. The file doesn't contain anything that needs to persist across reboots.
• ConEMU writes to the paste file and uses that instead.

This change has been "tested on my machine" and works.

[jpalardy]

hI @djhaskin987

thanks for the PR — I've left some comments inline

[jpalardy]

my initial reaction was resolve is probably too fast to benchmark (it's not in some inner loop) 🤔

but looking at the call sites, it wouldn't hurt to return paste_file -- so I think I'm OK with that 👍

I like checking for a writefile error, how about avoiding the result var? (it's only used for the if)

Suggested change

	let paste_file = slime#config#resolve("paste_file")
	let result = writefile(lines, paste_file, 'bS')
	if result != 0
	echoerr "Couldn't write to slime paste file."
	endif
	return paste_file
	let paste_file = slime#config#resolve("paste_file")
	if writefile(lines, paste_file, 'bS') != 0
	echoerr "Couldn't write to slime paste file."
	endif
	return paste_file

[jpalardy]

all in all, I'm surprised that using the pastefile would be faster than the clipboard … 🤔

---

The paste file has the S flag set, which tells vim not to bother calling fsync() on the file
…
The file doesn't contain anything that needs to persist across reboots.

That wasn't my understanding of fsync — doesn't that create a race-condition if we

1. write (but skip flush)
2. turn around and read the file

?

---

another concern is that the pastefile sticks around, holding on to your last slime send — I'm not sure everybody feels comfortable with that, so I've been avoiding it when possible (only screen was still using it, because there were no other choice 😮‍💨 )

[jpalardy]

@djhaskin987

any thoughts on this?