Don't pass read-file-name's result directly to git

When Magit is used with Tramp, read-file-name will return a path like
/ssh:host:/path/to/file.  The host part needs to be stripped before
passing the path to the host's git.  bf4332c fixed this issue for
magit-am-apply-{patches,maildir}.  This commit should take care of the
remaining places that call git with an unconverted read-file-name
result.

Follow the approach from bf4332c of converting a path at the time it
is passed to the git function rather than when it is returned by
read-file-name.  Note, however, that magit-file-rename is the only
function from bf4332c or this commit that makes use of the full
host:path, so it might make sense to add a function that wraps
(magit-read-file-name-convert (read-file-name ... )).

Re: #3368

Author: kyleam

lisp/magit-diff.el

@@ -982,8 +982,10 @@ be committed."
   (interactive (list (read-file-name "First file: " nil nil t)
                      (read-file-name "Second file: " nil nil t)))
   (magit-diff-setup nil (list "--no-index")
-                    nil (list (expand-file-name a)
-                              (expand-file-name b))))
+                    nil (list (magit-convert-filename-for-git
+                               (expand-file-name a))
+                              (magit-convert-filename-for-git
+                               (expand-file-name b)))))
 
 (defvar-local magit-buffer-revision-hash nil)
 

lisp/magit-files.el

@@ -352,13 +352,15 @@ If FILE isn't tracked in Git, fallback to using `rename-file'."
           (newname (read-file-name (format "Rename %s to file: " file))))
      (list (expand-file-name file (magit-toplevel))
            (expand-file-name newname))))
-  (if (magit-file-tracked-p file)
+  (if (magit-file-tracked-p (magit-convert-filename-for-git file))
       (let ((oldbuf (get-file-buffer file)))
         (when (and oldbuf (buffer-modified-p oldbuf))
           (user-error "Save %s before moving it" file))
         (when (file-exists-p newname)
           (user-error "%s already exists" newname))
-        (magit-run-git "mv" file newname)
+        (magit-run-git "mv"
+                       (magit-convert-filename-for-git file)
+                       (magit-convert-filename-for-git newname))
         (when oldbuf
           (with-current-buffer oldbuf
             (let ((buffer-read-only buffer-read-only))
@@ -493,7 +495,7 @@ If DEFAULT is non-nil, use this as the default value instead of
                                       (--when-let (magit-file-at-point)
                                         (file-relative-name it))))
                      (magit-patch-apply-arguments)))
-  (magit-run-git "apply" args "--" file))
+  (magit-run-git "apply" args "--" (magit-convert-filename-for-git file)))
 
 (defun magit-patch-save (file &optional arg)
   "Write current diff into patch FILE.