Julien Lepiller <julien@lepiller.eu> writes:

>>+etc/%.mount: etc/%.mount.in	\
>>+			 $(top_builddir)/config.status
>>+	$(AM_V_GEN)$(MKDIR_P) "`dirname $@`";	\
>>+	$(SED) -e 's|@''storedir''@|$(storedir)|' <	\
>>+	       "$<" > "$@.tmp";		\
>>+	mv "$@.tmp" "$@"
>> 
>> etc/guix-%.service: etc/guix-%.service.in	\
>> 			 $(top_builddir)/config.status
>
> I see that's how it's done with the existing service, but why sed the .in file when we could let configure.ac take care of it?

Because --storedir can in theory be something like '$prefix/store',
which would not get properly expanded by configure.  See "Installation
Directory Variables" in the GNU Autoconf manual:

  https://www.gnu.org/savannah-checkouts/gnu/autoconf/manual/autoconf-2.69/html_node/Installation-Directory-Variables.html

(in particular scroll down to the notice about AC_CONFIG_FILES)