Generate the documentation pages in the troff format

This commit introduces the `doc` target in the Makefile, which
generates man pages from the `asciidoc`-formatted documentation in the
`doc/manpages` directory.

Before being installed into the `$(sharedir)/doc` directory, the
generated raw man pages have to be striped of a few sections without
which `a2x` won't convert the `asciidoc` data: the shady block of shell
script in the `doc` target does just that, along with compressing the
resulting man page.

New dependency hereby introduced: `asciidoc`.

src/Makefile

@@ -20,6 +20,15 @@ endif
 sources := $(wildcard *.cc)
 objects := $(addprefix ., $(sources:.cc=$(suffix).o))
 deps := $(addprefix ., $(sources:.cc=$(suffix).d))
+docs := commands \
+		execeval \
+		expansions \
+		faces \
+		highlighters \
+		hooks \
+		options \
+		registers \
+		shortcuts \
 
 PREFIX ?= /usr/local
 DESTDIR ?= # root dir
@@ -63,20 +72,33 @@ kak : $(objects)
 .%$(suffix).o: %.cc
 	$(CXX) $(CPPFLAGS) $(CXXFLAGS) -MD -MP -MF $(addprefix ., $(<:.cc=$(suffix).d)) -c -o $@ $<
 
+%.1: %
+	a2x -f manpage $<
+%.1.gz: %.1.txt
+	a2x -f manpage $<
+	gzip -f $(basename $<)
+
 test:
 	cd ../test && ./run
 tags:
 	ctags -R
-man: ../doc/kakoune.1.txt
-	a2x -f manpage $<
-	gzip -fk $(basename $<)
+
+man: ../doc/kakoune.1.gz
+doc: $(addsuffix .1,$(addprefix ../doc/manpages/,$(docs)))
+	@for f in $^; do \
+		pagename="$${f##*/}"; pagename="$${pagename%.*}"; \
+		sed -i -r -e "s,^\.TH .+,.TH KAKOUNE 1 \"\" \"\" \"$${pagename^^}\"," \
+					-e "/^\.SH \"NAME\"/,+1d" $$f; \
+		gzip -f "$$f"; \
+		mv "$${f}.gz" "$${f/.1/}.gz"; \
+	done
 
 clean:
 	rm -f .*.o .*.d kak tags
 
 XDG_CONFIG_HOME ?= $(HOME)/.config
 
-install: kak man
+install: kak man doc
 	mkdir -p $(bindir)
 	install -m 0755 kak $(bindir)
 	mkdir -p $(sharedir)/rc