fix(git): cwd is sometimes required

Commit e0fe17114 ("fix(git show): allow cwd outside root git dir")
removed the "./" prefix before the filename when cwd did not equal the
root git dir.

Some aspects of VGit like live gutter and hunk preview rely on this, so
replace with self.cwd instead.

lua/vgit/git/cli/Git.lua

@@ -634,7 +634,7 @@ Git.show = loop.suspend(function(self, tracked_filename, commit_hash, spec, call
       '-C',
       self.cwd,
       'show',
-      string.format('%s:%s', commit_hash, tracked_filename),
+      string.format('%s:%s%s', commit_hash, self.cwd, tracked_filename),
     }),
     on_stdout = function(line) result[#result + 1] = line end,
     on_stderr = function(line) err[#err + 1] = line end,
@@ -658,7 +658,7 @@ Git.is_in_remote = loop.suspend(function(self, tracked_filename, commit_hash, sp
       '-C',
       self.cwd,
       'show',
-      string.format('%s:%s', commit_hash, tracked_filename),
+      string.format('%s:%s%s', commit_hash, self.cwd, tracked_filename),
     }),
     on_stderr = function(line)
       if line then