* emacs/guix-build-log.el (guix-build-log-minor-mode-activate): New variable.
(guix-build-log-minor-mode-activate-maybe): New function.
* emacs/guix-init.el: Add it to 'shell-mode-hook'.
* doc/emacs.texi (Emacs Build Log): Mention it.
* emacs/guix-build-log.el (guix-build-log-mode-hook): Remove
'compilation-shell-minor-mode' as it is slow on big buffers, and
'view-mode' as it rebinds too many keys.
(guix-build-log-mode-map): Add "c" and "v" key bindings for the
removed minor modes.
* emacs/guix-build-log.el (guix-build-log-mode-map): Move keys to ...
(guix-build-log-common-map): ...here. New variable.
(guix-build-log-minor-mode-map): New variable.
(guix-build-log-minor-mode): Use it.
* doc/emacs.texi (Emacs Build Log): Document it.
* emacs/guix-build-log.el (guix-build-log-phase-toggle-all): Handle the
case when there are no characters before the first phase:
'guix-build-log-next-phase' moves to the second phase in such a case,
and the toggling is not done properly, so use 're-search-forward'
instead.
