bug#69085: 29.2; Tramp: Extend tramp-make-copy-program-file-name via tramp-methods

[Sean Devlin]

Hi folks,

This is a feature request.

Tramp lets you define a method for out-of-band file copying with the
tramp-methods keys tramp-copy-program, tramp-copy-args, and so on.

Currently, there is no way to customize the format of remote file
paths. The function tramp-make-copy-program-file-name is responsible for
this job, and it is hard-coded to format files as USER@HOST:FILE.

I was working on a custom Tramp method, and I ran into problems setting
up OOB copying due to this limitation.

It would be great if there were a key you could set in tramp-methods to
override this logic. For example, maybe something like:

(tramp-copy-format-file-name my-tramp-make-copy-program-file-name)

Where my-tramp-make-copy-program-file-name is a function taking a vector
as input and returning a string of the formatted file name (similar to
tramp-make-copy-program-file-name).

Alternately, maybe a format string (or something similar to
tramp-login-args/tramp-copy-args) would be sufficient. In my case, I
just need to add a constant prefix to the remote file name, so a format
string would be fine.

Thanks!

In GNU Emacs 29.2 (build 1, aarch64-apple-darwin21.6.0, NS
appkit-2113.60 Version 12.6.6 (Build 21G646)) of 2024-01-18 built on
armbob.lan
Windowing system distributor 'Apple'
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