contrib/notmuch-mutt: add install target

The main goal here is to be able to install the notmuch-mutt script
with an absolute shebang. I have tried to make the notmuch-mutt
Makefile use configure information from notmuch if available, but make
suitable guesses if not.

contrib/notmuch-mutt/Makefile

@@ -1,5 +1,11 @@
 NAME = notmuch-mutt
 
+-include ../../Makefile.config
+PERL_ABSOLUTE ?= $(shell command -v perl 2>/dev/null)
+prefix ?= /usr/local
+sysconfdir ?= ${prefix}/etc
+mandir ?= ${prefix}/share/man
+
 all: $(NAME) $(NAME).1
 
 $(NAME).1: $(NAME)
@@ -8,5 +14,12 @@ $(NAME).1: $(NAME)
 README.html: README
 	markdown $< > $@
 
+install: all
+	mkdir -p $(DESTDIR)$(prefix)/bin
+	sed "1s|^#!.*|#! $(PERL_ABSOLUTE)|" < $(NAME) > $(DESTDIR)$(prefix)/bin/$(NAME)
+	chmod 755 $(DESTDIR)$(prefix)/bin/$(NAME)
+	install -D -m 644 $(NAME).1 $(DESTDIR)$(mandir)/man1/$(NAME).1
+	install -D -m 644 $(NAME).rc $(DESTDIR)$(sysconfdir)/Muttrc.d/$(NAME).rc
+
 clean:
 	rm -f notmuch-mutt.1 README.html