emacs: In 'run-with-store' call, specify the guile-for-build.

This fixes a regression introduced in commit e87f059.

* emacs/guix-main.scm (process-package-actions): Add call to
  'set-guile-for-build' in monadic expression.

Merge branch 'master' into 'core-updates'.

emacs: Handle autoloading Emacs packages installed with Guix.

* emacs/guix-emacs.el: New file.
* emacs.am (ELFILES): Add it.
* emacs/guix-backend.el (guix-after-repl-operation-hook): Add
  'guix-emacs-load-autoloads-maybe'.
* emacs/guix-init.el.in: Autoload emacs packages.
  (guix-package-enable-at-startup): New variable.

emacs: Move profiles code to "guix-profiles.el.in".

* emacs/guix-base.el (guix-user-profile, guix-default-profile,
  guix-current-profile, guix-profile-prompt, guix-set-current-profile): Move
  to...
* emacs/guix-init.el.in (guix-default-profile): Move to...
* emacs/guix-profiles.el.in: ... here.  New file.
* configure.ac (AC_CONFIG_FILES): Add "emacs/guix-profiles.el".
* emacs.am (nodist_lisp_DATA): Likewise.

emacs: Add missing directory to the guile load path.

Reported by Adam Pribyl and David Thompson.

* emacs/guix-helper.scm.in (set-paths!): Add guile module dir to '%load-path'.

emacs: Disable build traces produced by the daemon.

* emacs/guix-main.scm (process-package-actions,
  package-source-build-derivation): Pass #:print-build-trace #f to
  'set-build-options', to reduce verbosity.

emacs: Don't override the user's 'geiser-guile-load-path'.

* emacs/guix-backend.el (guix-start-repl): Add GUIX-LOAD-PATH to the
  front of GEISER-GUILE-LOAD-PATH instead of overriding it.

emacs: Add "Source" field to 'guix-info' buffers.

Suggested by Ludovic Courtès.

* emacs/guix-info.el (guix-info-insert-methods, guix-info-displayed-params):
  Add 'source' parameter.
  (guix-package-info-source): New face.
  (guix-package-source): New button type.
  (guix-package-info-auto-find-source, guix-package-info-auto-download-source,
  guix-package-info-download-buffer): New variables.
  (guix-package-info-show-source, guix-package-info-insert-source-url,
  guix-package-info-insert-source, guix-package-info-download-source,
  guix-package-info-redisplay-after-download): New procedures.
* emacs/guix-base.el (guix-param-titles): Add 'source' parameter.
  (guix-operation-prompt): Add 'prompt' argument.
  (guix-after-source-download-hook): New variable.
  (guix-package-source-path, guix-package-source-build-derivation): New
  procedures.
* emacs/guix-main.scm (%package-param-alist): Add 'source' parameter.
  (package-source-names, package-source-derivation->store-path,
  package-source-path, package-source-build-derivation): New procedures.

emacs: Improve 'guix-redisplay-buffer'.

* emacs/guix-base.el (guix-redisplay-buffer): Allow to display new entries.
  Restore point position.

emacs: Add 'guix-find-file'.

* emacs/guix-utils.el (guix-find-file): New procedure.
* emacs/guix-info.el (guix-file): Use it.

emacs: Restore mode-line after operation prompt.

* emacs/guix-base.el (guix-operation-prompt): Restore 'mode-line-format' after
  prompting.

emacs: Add "c" key binding to copy a button link.

* emacs/guix-info.el (guix-info-button-map): New variable.
  (guix-info-button-copy-label): New procedure.
* doc/emacs.texi (Emacs Info buffer): Mention a "c" key binding.
  (Emacs Keymaps): Add 'guix-info-button-map'.

emacs: Add 'guix-prettify'.

* emacs/guix-prettify.el: New file.
* emacs.am (ELFILES): Add it.
* doc/emacs.texi (Emacs Prettify): New node.
* doc/guix.texi (Features): Mention it.

emacs: Add interface for comparing generations.

Suggested by Ludovic Courtès.

* doc/emacs.texi (Emacs List buffer): Document new key bindings.
* emacs/guix-base.el (guix-generation-packages-buffer-name-function,
  guix-generation-packages-update-buffer, guix-output-name-width): New
  variables.
  (guix-generation-file, guix-manifest-file, guix-generation-packages,
  guix-generation-packages-buffer-name-default,
  guix-generation-packages-buffer-name-long,
  guix-generation-packages-buffer-name, guix-generation-packages-buffer,
  guix-generation-insert-package, guix-generation-insert-packages,
  guix-profile-generation-manifest-file,
  guix-profile-generation-packages-buffer): New procedures.
* emacs/guix-list.el: Add key bindings for comparing generations.
  (guix-generation-list-generations-to-compare,
  guix-generation-list-show-added-packages,
  guix-generation-list-show-removed-packages, guix-generation-list-compare,
  guix-generation-list-ediff-manifests, guix-generation-list-diff-manifests,
  guix-generation-list-ediff-packages, guix-generation-list-diff-packages,
  guix-generation-list-ediff, guix-generation-list-diff): New procedures.
* emacs/guix-messages.el (guix-messages): Add 'generation-diff' search type.
  (guix-message-outputs-by-diff): New procedure.
* emacs/guix-utils.el (guix-diff-switches): New variable.
  (guix-diff): New procedure.
* emacs/guix-main.scm (package/output-sexps): Handle 'generation-diff' search
  type.
  (manifest-entry->package-specification,
  manifest-entries->package-specifications, generation-package-specifications,
  generation-package-specifications+paths, generation-difference): New
  procedures.

emacs: Improve minibuffer messages.

* emacs/guix-base.el (guix-messages, guix-result-message): Move to
  'guix-messages.el'.
  (guix-set-buffer, guix-history-call, guix-redisplay-buffer): Adjust for
  the modified 'guix-result-message'.
* emacs/guix-messages.el: New file.
  (guix-redisplay-buffer): Add 'profile' argument.
  (guix-message-string-name, guix-message-string-entry-type,
  guix-message-string-entries, guix-message-packages-by-name,
  guix-message-generations-by-time): New procedures.

emacs: Add package info heading.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>

* emacs/guix-info.el: (guix-package-info-heading): New face.
  (guix-package-info-synopsis): Modify face.
  (guix-info-insert-entry-default, guix-package-info-insert-heading,
  guix-package-info-insert-with-heading): New procedures.
  (guix-package-info-heading-params, guix-info-insert-package-function,
  guix-info-insert-installed-function, guix-info-insert-output-function,
  guix-info-insert-generation-function): New variables.

emacs: Add 'guix-pull' command.

* emacs/guix-base.el (guix-pull): New command.
  (guix-update-after-pull, guix-after-pull-hook): New variables.
  (guix-restart-repl-after-pull, guix-update-buffers-maybe-after-pull): New
  procedures.
* emacs/guix-main.scm: Use (guix scripts pull) module.
* doc/emacs.texi (Emacs Commands): Document 'guix-pull' command.

emacs: Improve REPL procedures.

* emacs/guix-backend.el (guix-start-process-maybe): Add 'start-msg' and
  'end-msg' optional arguments.
  (guix-start-repl-maybe): Likewise.  Do not kill buffer with a dead process.
  (guix-repl-exit): New procedure.
  (guix-eval-in-repl): Use 'geiser-repl--send'.

emacs: Improve buffer procedures.

* emacs/guix-base.el (guix-list-or-info-buffer-p): Delete.  Replace with...
  (guix-buffer-p): ... this.  New procedure.
  (guix-buffers): Use it.  Add 'modes' argument.
  (guix-update-buffer): New procedure.
  (guix-update-buffers-maybe): Rename to ...
  (guix-update-buffers-maybe-after-operation): this.  Use
  'guix-update-buffer'.

emacs: Introduce REPL operation type.

* emacs/guix-backend.el (guix-repl-operation-type): New variable.
  (guix-repl-output-filter): Run type hooks after performing an operation.
  (guix-eval-read): Add 'operation-type' argument.