>     I have appended a patch which should fix the problem. Could you,
>     please, (let) test?
>
> Great, I'll make them test & report (or test myself if needed).

FTR, this morning I've made a test with a cloned Linux kernel git repo
(66473 files). I've accessed the directory via "/ssh::".
(shell-command-to-string "git ls-files -zco --exclude-standard")
returned in a few seconds, with a line of 2479486 bytes.

I've committed the patch meanwhile. Tramp 2.4.3, scheduled for end of
the year, will contain it.

In case there's a problem, you still have some days to report :-)