editor: use canonicalized absolute path

By improving the relative_path() algorithm, e02ca72 (path.c:
refactor relative_path(), not only strip prefix, 2013-06-25)
uncovered a latent bug in Emacs.  While most editor applications
like cat and vim handle non-canonicalized relative paths fine, emacs
does not.  This is due to a long-standing bug in emacs, where it
refuses to resolve symlinks in the supplied path:

#!/bin/sh
cd /tmp
mkdir z z/a z/b
echo moodle >z/a/file
ln -s z/b
cd b
emacs ../a/file # fail: attempts to open /tmp/a/file

Even if emacs were to be patched to fix this bug, it may be nicer to
help users running older versions.

Note that this can potentially regress for users of all editors,
when they ask "what file am I editing?" to the editor, as it is
likely to answer with an unsightly long full path.

Co-authored-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/editor.c b/editor.c
index 27bdecdaf3d99d3179737e07be971d2458408660..0abbd8dc3a0ec91acd0c143b6d9b5ad41ac90417 100644 (file)
--- a/editor.c
+++ b/editor.c
@@ -37,7 +37,7 @@ int launch_editor(const char *path, struct strbuf *buffer, const char *const *en
                return error("Terminal is dumb, but EDITOR unset");
 
        if (strcmp(editor, ":")) {
-               const char *args[] = { editor, path, NULL };
+               const char *args[] = { editor, real_path(path), NULL };
                struct child_process p;
                int ret, sig;