Move some variable assignments from Makefile.local to Makefile.config

There's not any special configure logic for determining these variable
values, but if we did add some in the future, then these will now be
in the right place for that.

Additionally, this now makes Makefile.local the single place for the
user to look for manually tweaking a variable assignment, (say, for a
compiler that can't accept a particular warning argument).

With this change, there should rarely be any need for a user to poke
into any Makefile.local file.

Makefile.local

@@ -12,10 +12,6 @@ Makefile.config: configure
 	@echo ""
 	./configure
 
-SONAME = libnotmuch.so.1
-WARN_CXXFLAGS=-Wall -Wextra -Wwrite-strings -Wswitch-enum
-WARN_CFLAGS=$(WARN_CXXFLAGS) -Wmissing-declarations
-
 # Sub-directory Makefile.local fragments can append to these variables
 # to have directory-specific cflags as necessary.
 extra_cflags :=
@@ -26,15 +22,6 @@ FINAL_CFLAGS = $(CFLAGS) $(WARN_CFLAGS) $(CONFIGURE_CFLAGS) $(extra_cflags)
 FINAL_CXXFLAGS = $(CXXFLAGS) $(WARN_CXXFLAGS) $(CONFIGURE_CXXFLAGS) $(extra_cflags) $(extra_cxxflags)
 FINAL_LDFLAGS = $(LDFLAGS) $(CONFIGURE_LDFLAGS)
 
-# Additional programs that are used during the compilation process.
-EMACS ?= emacs --quick
-# Lowercase to avoid clash with GZIP environment variable for passing
-# arguments to gzip.
-gzip = gzip
-
-bash_completion_dir = /etc/bash_completion.d
-zsh_completion_dir = /usr/share/zsh/functions/Completion/Unix
-
 all: notmuch notmuch.1.gz
 ifeq ($(MAKECMDGOALS),)
 	@echo ""
@@ -117,6 +104,8 @@ notmuch: $(notmuch_client_modules) lib/libnotmuch.so
 notmuch.1.gz: notmuch.1
 	$(call quiet,gzip) --stdout $^ > $@
 
+SONAME = libnotmuch.so.1
+
 install: all notmuch.1.gz
 	for d in $(DESTDIR)$(prefix)/bin/ $(DESTDIR)$(libdir)/ \
 		$(DESTDIR)$(prefix)/include/ $(DESTDIR)$(prefix)/share/man/man1 ; \

configure

@@ -8,6 +8,13 @@ CFLAGS=${CFLAGS:--O2}
 CXXFLAGS=${CXXFLAGS:-\$(CFLAGS)}
 XAPIAN_CONFIG=${XAPIAN_CONFIG:-xapian-config-1.1 xapian-config}
 
+# We don't allow the EMACS or GZIP Makefile variables inherit values
+# from the environment as we do with CC and CXX above. The reason is
+# that these names as environment variables have existing uses other
+# than the program name that we want. (EMACS is set to 't' when a
+# shell is running within emacs and GZIP specifies arguments to pass
+# on the gzip command line).
+
 # Set the defaults for values the user can specify with command-line
 # options.
 PREFIX=/usr/local
@@ -269,12 +276,24 @@ CC = ${CC}
 # The C++ compiler to use
 CXX = ${CXX}
 
+# Command to execute emacs from Makefiles
+EMACS = emacs --quick
+
+# Command to execute gzip from Makefiles
+gzip = gzip
+
 # Default FLAGS for C compiler (can be overridden by user such as "make CFLAGS=-g")
 CFLAGS = ${CFLAGS}
 
 # Default FLAGS for C++ compiler (can be overridden by user such as "make CXXFLAGS=-g")
 CXXFLAGS = ${CXXFLAGS}
 
+# Flags to enable warnings when using the C++ compiler
+WARN_CXXFLAGS=-Wall -Wextra -Wwrite-strings -Wswitch-enum
+
+# Flags to enable warnings when using the C compiler
+WARN_CFLAGS=\$(WARN_CXXFLAGS) -Wmissing-declarations
+
 # The prefix to which notmuch should be installed
 prefix = ${PREFIX}
 
@@ -287,6 +306,12 @@ emacs_lispdir=${emacs_lispdir}
 # The directory to which desktop files should be installed
 desktop_dir = \${prefix}/share/applications
 
+# The directory to which bash completions files should be installed
+bash_completion_dir = /etc/bash_completion.d
+
+# The directory to which zsh completions files should be installed
+zsh_completion_dir = ${PREFIX}/share/zsh/functions/Completion/Unix
+
 # Whether the getline function is available (if not, then notmuch will
 # build its own version)
 HAVE_GETLINE = ${have_getline}