Provide branch information for both Emacs and Tramp (Bug#33328)

Provide branch information for both Emacs and Tramp (Bug#33328)

* doc/lispref/intro.texi (Version Info):
Document `emacs-repository-version' and `emacs-repository-branch'.

* etc/NEWS: Mention `emacs-repository-branch'.

* lisp/loadup.el: Initialize `emacs-repository-branch'.

* lisp/version.el (emacs-repository-branch): New variable.
(emacs-repository-branch-git, emacs-repository-get-branch):
New defuns.

* lisp/mail/emacsbug.el (report-emacs-bug):
Insert `emacs-repository-branch'.

* lisp/net/tramp.el (tramp-get-local-gid):
Use `group-name' if available.
(tramp-debug-message):
* lisp/net/tramp-cmds.el (tramp-bug): Report also
`tramp-repository-branch' and `tramp-repository-version'.

* lisp/net/trampver.el (tramp-repository-branch)
(tramp-repository-version): New defconst.
(tramp-repository-get-version): Remove.