Include a systemd user unit file. (Bug#16507)

* etc/emacs.service: New file.
* doc/emacs/misc.texi (Emacs Server): Mention systemcl --user.
* Makefile.in (libdir): New, set by configure.
(systemdunitdir): New variable.
(install-etc, uninstall): Handle the emacs.service file.

Makefile.in

@@ -153,6 +153,9 @@ sharedstatedir=@sharedstatedir@
 # a subdirectory of this.
 libexecdir=@libexecdir@
 
+# Currently only used for the systemd service file.
+libdir=@libdir@
+
 # Where to install Emacs's man pages.
 # Note they contain cross-references that expect them to be in section 1.
 mandir=@mandir@
@@ -196,6 +199,17 @@ desktopdir=$(datarootdir)/applications
 # Where the etc/emacs.appdata.xml file is to be installed.
 appdatadir=$(datarootdir)/appdata
 
+# Where the etc/emacs.service file is to be installed.
+# The system value (typically /usr/lib/systemd/user) can be
+# obtained with: pkg-config --variable=systemduserunitdir systemd
+# but that does not respect configure's prefix.
+# It is not clear where we should install this file when
+# prefix != /usr (or /usr/local?) (eg for non-root installs).
+# Other options include ~/.config/systemd/user/,
+# $XDG_RUNTIME_DIR/systemd/user/
+# It seems the user may end up having to make a manual link...
+systemdunitdir=$(libdir)/systemd/user
+
 # Where the etc/images/icons/hicolor directory is to be installed.
 icondir=$(datarootdir)/icons
 
@@ -714,6 +728,18 @@ install-etc:
 	  ${srcdir}/etc/emacs.appdata.xml > $${tmp}; \
 	${INSTALL_DATA} $${tmp} "$(DESTDIR)${appdatadir}/${EMACS_NAME}.appdata.xml"; \
 	rm -f $${tmp}
+	umask 022; $(MKDIR_P) "$(DESTDIR)$(systemdunitdir)"
+	tmp=etc/emacs.tmpservice; rm -f $${tmp}; \
+	emacs_name=`echo emacs | sed '$(TRANSFORM)'`; \
+	exe_name=$${emacs_name}${EXEEXT}; \
+	client_name=`echo emacsclient | sed '$(TRANSFORM)'`${EXEEXT}; \
+	sed -e '/^##/d' \
+	  -e "/^Documentation/ s/emacs(1)/$${emacs_name}(1)/" \
+	  -e "/^ExecStart/ s|emacs|$(DESTDIR)${bindir}/$${exe_name}|" \
+	  -e "/^ExecStop/ s|emacsclient|$(DESTDIR)${bindir}/$${client_name}|" \
+	  ${srcdir}/etc/emacs.service > $${tmp}; \
+	$(INSTALL_DATA) $${tmp} "$(DESTDIR)$(systemdunitdir)/${EMACS_NAME}.service"; \
+	rm -f $${tmp}
 	thisdir=`/bin/pwd`; \
 	cd ${iconsrcdir} || exit 1; umask 022 ; \
 	for dir in */*/apps */*/mimetypes; do \
@@ -779,6 +805,7 @@ uninstall: uninstall-$(NTDIR) uninstall-doc
 	fi)
 	-rm -f "$(DESTDIR)${desktopdir}/${EMACS_NAME}.desktop"
 	-rm -f "$(DESTDIR)${appdatadir}/${EMACS_NAME}.appdata.xml"
+	-rm -f "$(DESTDIR)$(systemdunitdir)/${EMACS_NAME}.service"
 	for file in snake-scores tetris-scores; do \
 	  file="$(DESTDIR)${gamedir}/$${file}"; \
 	  [ -s "$${file}" ] || rm -f "$$file"; \

doc/emacs/misc.texi

@@ -1570,7 +1570,7 @@ process.
 
   You can solve this problem by setting up Emacs as an @dfn{edit
 server}, so that it ``listens'' for external edit requests and acts
-accordingly.  There are two ways to start an Emacs server:
+accordingly.  There are various ways to start an Emacs server:
 
 @itemize
 @findex server-start
@@ -1589,32 +1589,29 @@ calls @code{server-start} after initialization, and returns control to
 the calling terminal instead of opening an initial frame; it then
 waits in the background, listening for edit requests.
 
+@cindex systemd unit file
+@item
+If your operating system uses @command{systemd} to manage startup,
+you can automatically start Emacs in daemon mode when you login
+using the supplied @dfn{systemd unit file}.  To activate this:
+@example
+systemctl --user enable emacs
+@end example
+(If your Emacs was installed into a non-standard location, you may
+need to copy the @file{emacs.service} file to a standard directory
+such as @file{~/.config/systemd/user/}.)
+
 @cindex socket activation, systemd, Emacs
 @item
 An external process can invoke the Emacs server when a connection
 event occurs upon a specified socket and pass the socket to the new
-Emacs server process.  An instance of this is @command{systemd}'s
+Emacs server process.  An instance of this is the socket functionality
-socket functionality: the @command{systemd} service creates a socket and
+of @command{systemd}: the @command{systemd} service creates a socket and
 listens for connections on it; when @command{emacsclient} connects to
 it for the first time, @command{systemd} can launch the Emacs server
 and hand over the socket to it for servicing @command{emacsclient}
 connections.  A setup to use this functionality could be:
 
-@file{~/.config/systemd/user/emacs.service}:
-@example
-[Unit]
-Description=Emacs
-
-[Service]
-Type=forking
-ExecStart=/path/to/emacs --daemon
-ExecStop=/path/to/emacsclient --eval "(kill-emacs)"
-Restart=always
-
-[Install]
-WantedBy=default.target
-@end example
-
 @file{~/.config/systemd/user/emacs.socket}:
 @example
 [Socket]
@@ -1624,12 +1621,14 @@ ListenStream=/path/to/.emacs.socket
 WantedBy=sockets.target
 @end example
 
+(The @file{emacs.service} file described above must also be installed.)
+
 The @code{ListenStream} path will be the path that Emacs listens for
 connections from @command{emacsclient}; this is a file of your choice.
 @end itemize
 
 @cindex @env{TEXEDIT} environment variable
-  Either way, once an Emacs server is started, you can use a shell
+  Once an Emacs server is started, you can use a shell
 command called @command{emacsclient} to connect to the Emacs process
 and tell it to visit a file.  You can then set the @env{EDITOR}
 environment variable to @samp{emacsclient}, so that external programs

etc/NEWS

@@ -44,6 +44,12 @@ hand the socket over to Emacs.  Emacs uses this socket to service
 emacsclient commands.  This new functionality can be disabled with the
 configure option '--disable-libsystemd'.
 
++++
+** A systemd user unit file is provided.  Use it in the standard way:
+systemctl --user enable emacs
+(If your Emacs is installed in a non-standard location, you may
+need to copy the emacs.service file to eg ~/.config/systemd/user/)
+
 ** New configure option '--disable-build-details' attempts to build an
 Emacs that is more likely to be reproducible; that is, if you build
 and install Emacs twice, the second Emacs is a copy of the first.

etc/emacs.service

@@ -0,0 +1,17 @@
+## If your Emacs is installed in a non-standard location, you may need
+## to copy this file to a standard directory, eg ~/.config/systemd/user/ .
+## If you install this file by hand, change the "Exec" lines below
+## to use absolute file names for the executables.
+[Unit]
+Description=Emacs text editor
+Documentation=info:emacs man:emacs(1) https://gnu.org/software/emacs/
+
+[Service]
+Type=forking
+ExecStart=emacs --daemon
+ExecStop=emacsclient --eval "(kill-emacs)"
+Environment=SSH_AUTH_SOCK=%t/keyring/ssh
+Restart=on-failure
+
+[Install]
+WantedBy=default.target