Fix CD argument behavior of dz-defservice

[tkf]

Specifying CD argument when using dz-defservice macro causes
NAME-start function to move the directory of the current buffer.
This problem is fixed by simply replacing dz-dir-excursion with
a let clause where default-directory is dynamically bound to CD.

[maio]

Would this get merged into master someday? Changing directory of currently edited file is pretty annoying.

[bovid-19]

@davidmiller Is there a reason dz-dir-excursion is required?

The way I understand the documentation for the :cd keyword*, the patched version should be correct and it arguably makes the code easier to read.

If this wasn't an oversight and the patch doesn't work for you, would you merge one that adds this behaviour through another keyword, e.g. :dir, :path or :data?

---

* :cd - (string) The directory in which you would like the service to run

[camachojua]

I've recently forked this repo and I've started to update some deprecated functions (as per emacs 29) @tkf would you mind to point your PR to my fork? In this way we can start updating this amazing package

[gopar]

Welps, guessing this aint getting merged anytime soon. I manually edited the file. Not great but its better than nothing.