Support tramp connections (e.g. log in with another user and run `git grep` though it)

[clemente]

I sometimes log in to my localhost through another user, with tramp.
For instance, (find-file "/su:user2@:/home/user2/").
Then I go a a git repository inside that folder, and want to use helm-git-grep there.

Currently it doesn't work: it tries to run git grep with my main user, not with user2. It should do the su user2 first and run git grep as user2.

Tested in:

;; Version: 0.10.1
;; Package-Version: 20170614.1411

GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 1.16.0, Xaw scroll bars) of 2022-10-28`

[clemente]

This is a first step, that works.

(defun helm-git-grep-process ()
  "Retrieve candidates from result of git grep.
It decides whether to use tramp or not, based on the directory.

It's just a proof of concept, to show that it's possible to make helm-git-grep work with tramp.
It shows more debug messages than required and IT DOESN'T CLOSE PROCESSES, so you'll be left
with many `su' processes. You may manually kill them.
But it works: it allows you to e.g. open this path:
/su:user2@:/home/user2/
and then helm-git-grep will run `git grep' as that user. Non-tramp paths aren't affected.

Please improve this function and post a fixed version!"
  (helm-aif (helm-attr 'base-directory)
      (let* ((default-directory it)
			 (handler (find-file-name-handler (directory-file-name default-directory)
											  'make-process)))
        (make-process
         :name "git-grep-process"
         :buffer "*debuggingbuffer1*"
         :command (append '("git") (helm-git-grep-args))
         :file-handler handler
         )) '()))

[clemente]

The previous code uses make-process instead of the start-process currently used by helm-git-grep
.
make-process supports tramp, though I think it's only in Emacs 27 (from August 2020) or newer