doc: cookbook: Fix overlong lines.

Fixes <https://issues.guix.gnu.org/63680>.

Thanks to Nigko Yerden for telling me ExecStart lines can be multi-line
<https://lists.gnu.org/archive/html/bug-guix/2024-05/msg00153.html>.

* doc/guix-cookbook.texi (System Configuration)
[Customizing the Kernel]: Split lines.
[Customizing a Window Manager]<StumpWM>: Likewise.
[Setting up a bind mount]: Move comments.
[Getting substitutes from Tor]: Split line with backslash.
[Music Server with Bluetooth Audio]: Likewise.
(Advanced package management)[Guix Profiles in Practice]
<Basic setup with manifests>: Likewise.
<Reproducible profiles>: Likewise.
(Environment management)[Guix environment via direnv]: Likewise.
(Installing Guix on a Cluster)[Setting Up a Head Node]:
On Info and PDF, split ExecStart= command with backslash.

Change-Id: I31ef5b0417b319c3f6946d65f83edafb86c8f36b

doc/guix-cookbook.texi

@@ -23,7 +23,8 @@ Copyright @copyright{} 2020 Christine Lemmer-Webber@*
 Copyright @copyright{} 2021 Joshua Branson@*
 Copyright @copyright{} 2022, 2023 Maxim Cournoyer@*
 Copyright @copyright{} 2023-2024 Ludovic Courtès@*
-Copyright @copyright{} 2023 Thomas Ieong
+Copyright @copyright{} 2023 Thomas Ieong@*
+Copyright @copyright{} 2024 Florian Pelz@*
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -1693,7 +1694,8 @@ declared like this:
   (make-linux-libre* linux-libre-5.15-version
                      linux-libre-5.15-gnu-revision
                      linux-libre-5.15-source
-                     '("x86_64-linux" "i686-linux" "armhf-linux" "aarch64-linux" "riscv64-linux")
+                     '("x86_64-linux" "i686-linux" "armhf-linux"
+                       "aarch64-linux" "riscv64-linux")
                      #:configuration-file kernel-config))
 @end lisp
 
@@ -2405,9 +2407,11 @@ Then you need to add the following code to a StumpWM configuration file
 @lisp
 (require :ttf-fonts)
 (setf xft:*font-dirs* '("/run/current-system/profile/share/fonts/"))
-(setf clx-truetype:+font-cache-filename+ (concat (getenv "HOME") "/.fonts/font-cache.sexp"))
+(setf clx-truetype:+font-cache-filename+ (concat (getenv "HOME")
+                                                 "/.fonts/font-cache.sexp"))
 (xft:cache-fonts)
-(set-font (make-instance 'xft:font :family "DejaVu Sans Mono" :subfamily "Book" :size 11))
+(set-font (make-instance 'xft:font :family "DejaVu Sans Mono"
+                                   :subfamily "Book" :size 11))
 @end lisp
 
 @node Session lock
@@ -2963,13 +2967,14 @@ should be defined, so that the bind mount can depend on it.
    (file-system
     (device (uuid "UUID goes here"))
     (mount-point "/path-to-spinning-disk-goes-here")
-    (type "ext4"))) ;; Make sure to set this to the appropriate type for your drive.
+    (type "ext4"))) ;Make sure to set this to the appropriate type for your drive.
 @end lisp
 
 The source folder must also be defined, so that guix will know it's not
 a regular block device, but a folder.
 @lisp
-(define (%source-directory) "/path-to-spinning-disk-goes-here/tmp") ;; "source-directory" can be named any valid variable name.
+;; "source-directory" can be named any valid variable name.
+(define (%source-directory) "/path-to-spinning-disk-goes-here/tmp")
 @end lisp
 
 Finally, inside the @code{file-systems} definition, we must add the
@@ -2980,14 +2985,18 @@ mount itself.
 
                 ...<other drives omitted for clarity>...
 
-                source-drive ;; Must match the name you gave the source drive in the earlier definition.
+                ;; Must match the name you gave the source drive in the earlier definition.
+                source-drive
 
                 (file-system
-                 (device (%source-directory)) ;; Make sure "source-directory" matches your earlier definition.
+                 ;; Make sure "source-directory" matches your earlier definition.
+                 (device (%source-directory))
                  (mount-point "/tmp")
-                 (type "none") ;; We are mounting a folder, not a partition, so this type needs to be "none"
+                 ;; We are mounting a folder, not a partition, so this type needs to be "none"
+                 (type "none")
                  (flags '(bind-mount))
-                 (dependencies (list source-drive)) ;; Ensure "source-drive" matches what you've named the variable for the drive.
+                 ;; Ensure "source-drive" matches what you've named the variable for the drive.
+                 (dependencies (list source-drive))
                  )
 
                  ...<other drives omitted for clarity>...
@@ -3036,8 +3045,8 @@ follow:
           config => (guix-configuration
                       (inherit config)
                       ;; ci.guix.gnu.org's Onion service
-                      (substitute-urls
+                      (substitute-urls "\
-                       "@value{SUBSTITUTE-TOR-URL}")
+@value{SUBSTITUTE-TOR-URL}")
                       (http-proxy "http://localhost:9250")))))))
 @end lisp
 
@@ -3279,12 +3288,14 @@ that should accomplish the above-mentioned tasks:
               #~(string-append "\
 # Declare Bluetooth audio device type \"bluealsa\" from bluealsa module
 pcm_type.bluealsa @{
-    lib \"" #$(file-append bluez-alsa "/lib/alsa-lib/libasound_module_pcm_bluealsa.so") "\"
+    lib \""
+#$(file-append bluez-alsa "/lib/alsa-lib/libasound_module_pcm_bluealsa.so") "\"
 @}
 
 # Declare control device type \"bluealsa\" from the same module
 ctl_type.bluealsa @{
-    lib \"" #$(file-append bluez-alsa "/lib/alsa-lib/libasound_module_ctl_bluealsa.so") "\"
+    lib \""
+#$(file-append bluez-alsa "/lib/alsa-lib/libasound_module_ctl_bluealsa.so") "\"
 @}
 
 # Define the actual Bluetooth audio device.
@@ -4076,7 +4087,8 @@ We can create a manifest specification per profile and install them this way:
 @example
 GUIX_EXTRA_PROFILES=$HOME/.guix-extra-profiles
 mkdir -p "$GUIX_EXTRA_PROFILES"/my-project # if it does not exist yet
-guix package --manifest=/path/to/guix-my-project-manifest.scm --profile="$GUIX_EXTRA_PROFILES"/my-project/my-project
+guix package --manifest=/path/to/guix-my-project-manifest.scm \
+ --profile="$GUIX_EXTRA_PROFILES"/my-project/my-project
 @end example
 
 Here we set an arbitrary variable @samp{GUIX_EXTRA_PROFILES} to point to the directory
@@ -4149,7 +4161,8 @@ for the command line options.
 To upgrade a profile, simply install the manifest again:
 
 @example
-guix package -m /path/to/guix-my-project-manifest.scm -p "$GUIX_EXTRA_PROFILES"/my-project/my-project
+guix package -m /path/to/guix-my-project-manifest.scm \
+ -p "$GUIX_EXTRA_PROFILES"/my-project/my-project
 @end example
 
 To upgrade all profiles, it's easy enough to loop over them.  For instance,
@@ -4159,7 +4172,8 @@ of the profile (e.g.@: "project1"), you could do the following in Bourne shell:
 
 @example
 for profile in "$GUIX_EXTRA_PROFILES"/*; do
-  guix package --profile="$profile" --manifest="$HOME/.guix-manifests/guix-$profile-manifest.scm"
+  guix package --profile="$profile" \
+   --manifest="$HOME/.guix-manifests/guix-$profile-manifest.scm"
 done
 @end example
 
@@ -4337,7 +4351,9 @@ mkdir -p "$GUIX_EXTRA"/my-project
 guix pull --channels=channel-specs.scm --profile="$GUIX_EXTRA/my-project/guix"
 
 mkdir -p "$GUIX_EXTRA_PROFILES/my-project"
-"$GUIX_EXTRA"/my-project/guix/bin/guix package --manifest=/path/to/guix-my-project-manifest.scm --profile="$GUIX_EXTRA_PROFILES"/my-project/my-project
+"$GUIX_EXTRA"/my-project/guix/bin/guix package \
+ --manifest=/path/to/guix-my-project-manifest.scm \
+ --profile="$GUIX_EXTRA_PROFILES"/my-project/my-project
 @end example
 
 It's safe to delete the Guix channel profile you've just installed with the
@@ -5071,7 +5087,8 @@ use_guix()
     PACKAGES=(help2man guile-sqlite3 guile-gcrypt)
 
     # Thanks <https://lists.gnu.org/archive/html/guix-devel/2016-09/msg00859.html>
-    eval "$(guix environment --search-paths --root="$gcroot" --pure guix --ad-hoc $@{PACKAGES[@@]@} $@{PACKAGES_MAINTENANCE[@@]@} "$@@")"
+    eval "$(guix shell --search-paths --root="$gcroot" --pure guix \
+     $@{PACKAGES[@@]@} $@{PACKAGES_MAINTENANCE[@@]@} "$@@")"
 
     # Predefine configure flags.
     configure()
@@ -5178,9 +5195,21 @@ startup file for @command{guix-daemon},
 @code{--listen} argument to the @code{ExecStart} line so that it looks
 something like this:
 
+@c Since Debian Buster, \ is documented to split lines.
+@c https://manpages.debian.org/buster/systemd/systemd.exec.5.en.html
+@c Use it in PDF and Info versions to avoid cut-off at the page border.
+@ifnothtml
+@example
+ExecStart=/var/guix/profiles/per-user/root/current-guix/bin/guix-daemon \
+    --build-users-group=guixbuild \
+    --listen=/var/guix/daemon-socket/socket --listen=0.0.0.0
+@end example
+@end ifnothtml
+@ifhtml
 @example
 ExecStart=/var/guix/profiles/per-user/root/current-guix/bin/guix-daemon --build-users-group=guixbuild --listen=/var/guix/daemon-socket/socket --listen=0.0.0.0
 @end example
+@end ifhtml
 
 For these changes to take effect, the service needs to be restarted: