Documentation: Allow to use asciidoctor for formatting man pages

Since asciidoc is based on Phyton 2, we want to move to alternative,
and a promising one is asciidoctor.  This patch allows to use
asciidoctor for formatting man pages instead of asiidoc, by passing
a make option, USE_ASCIIDOCTOR=yes.

Although asciidoctor is almost compatible with asciidoc, it can
produce a man page directly from a text file without XML, which is
more efficiently.  So in asciidoctor mode, we don't require xmlto.
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Andrei Vagin <avagin@gmail.com>

Documentation/Makefile

@@ -2,8 +2,13 @@ __nmk_dir ?= ../scripts/nmk/scripts/
 include $(__nmk_dir)include.mk
 include $(__nmk_dir)macro.mk
 
+ifneq ($(USE_ASCIIDOCTOR),)
+ASCIIDOC	:= asciidoctor
+XMLTO		:=
+else
 ASCIIDOC	:= asciidoc
 XMLTO		:= xmlto
+endif
 
 FOOTER		:= footer.txt
 SRC1		+= crit.txt
@@ -44,13 +49,21 @@ $(FOOTER): ../Makefile.versions
 
 %.1: %.txt $(FOOTER) custom.xsl
 	$(call msg-gen, $@)
+ifneq ($(USE_ASCIIDOCTOR),)
+	$(Q) $(ASCIIDOC) -b manpage -d manpage -o $@ $<
+else
 	$(Q) $(ASCIIDOC) -b docbook -d manpage -o $(patsubst %.1,%.xml,$@) $<
 	$(Q) $(XMLTO) man -m custom.xsl $(patsubst %.1,%.xml,$@) 2>/dev/null
+endif
 
 %.8: %.txt $(FOOTER) custom.xsl
 	$(call msg-gen, $@)
+ifneq ($(USE_ASCIIDOCTOR),)
+	$(Q) $(ASCIIDOC) -b manpage -d manpage -o $@ $<
+else
 	$(Q) $(ASCIIDOC) -b docbook -d manpage -o $(patsubst %.8,%.xml,$@) $<
 	$(Q) $(XMLTO) man -m custom.xsl $(patsubst %.8,%.xml,$@) 2>/dev/null
+endif
 
 %.ps: %.1
 	$(call msg-gen, $@)

scripts/nmk/Documentation/Makefile

+ifneq ($(USE_ASCIIDOCTOR),)
+ASCIIDOC       := asciidoctor
+XMLTO          :=
+else
 ASCIIDOC	:= asciidoc
 XMLTO		:= xmlto
+endif
 PS2PDF		:= ps2pdf
 
 SRC		+= nmk.txt
@@ -25,8 +30,12 @@ check:
 
 %.8: %.txt
 	$(call msg-gen, $@)
+ifneq ($(USE_ASCIIDOCTOR),)
+	$(Q) $(ASCIIDOC) -b manpage -d manpage -o $@ $<
+else
 	$(Q) $(ASCIIDOC) -b docbook -d manpage -o $(patsubst %.8,%.xml,$@) $<
 	$(Q) $(XMLTO) man --skip-validation $(patsubst %.8,%.xml,$@) 2>/dev/null
+endif
 
 %.ps: %.8
 	$(call msg-gen, $@)

test/others/bers/Makefile

@@ -8,8 +8,13 @@ endif
 
 export E Q
 
+ifneq ($(USE_ASCIIDOCTOR),)
+ASCIIDOC       := asciidoctor
+XMLTO          :=
+else
 ASCIIDOC	:= asciidoc
 XMLTO		:= xmlto
+endif
 
 SRC		+= bers.txt
 XMLS		:= $(patsubst %.txt,%.xml,$(SRC))
@@ -17,8 +22,12 @@ MANS		:= $(patsubst %.txt,%.8,$(SRC))
 
 %.8: %.txt
 	$(E) "  GEN     " $@
+ifneq ($(USE_ASCIIDOCTOR),)
+	$(Q) $(ASCIIDOC) -b manpage -d manpage -o $@ $<
+else
 	$(Q) $(ASCIIDOC) -b docbook -d manpage -o $(patsubst %.8,%.xml,$@) $<
 	$(Q) $(XMLTO) man --skip-validation $(patsubst %.8,%.xml,$@) 2>/dev/null
+endif
 
 docs: $(MANS)
 	@true