bug#43164: 26.3.50; project.el still broken under Emacs 26.3

[João Távora]

João Távora <joaotavora@gmail.com> writes:

> João Távora <joaotavora@gmail.com> writes:
>
>> This is breaking Eglot for Emacs 26.3 users:
>> https://github.com/joaotavora/eglot/issues/530
>
> Over there, Andrii Kolomoiets has identified the culprit commit:
> http://git.savannah.gnu.org/cgit/emacs.git/commit/?id=b63c5a7efc89c23230f53a346e29e72a9b4faafc

I fixed this in 5142149758333cfddc25c8c696e0e6f322e37d62, by not adding
the keybinding to a non-existing keymap.  I tested merely by loading the
project.el file in Emacs 26.3 and checking it loaded OK.  I bumped the
version to 0.5.2 and it should be in GNU ELPA soon.

Directly calling M-x project-other-tab-command in Emacs 26.3 will still
fail, but that's not a show-stopping bug as this one was.

In the future, we must make sure to honour the advice in the file's
header:

   ;; Package-Requires: ((emacs "26.3") (xref "1.0.2"))
    
   ;; This is a GNU ELPA :core package.  Avoid using functionality that
   ;; not compatible with the version of Emacs recorded above.

João