Add version information to man pages

Inspired and copied from git 7ef195ba3efe0ffa815e12afc4cb1e39a21ddfb4:

    Override the [header] macro of asciidoc's docbook
    backend to add version information to the generated
    man pages.

by Frank Lichtenheld <frank@lichtenheld.de>. Slightly improved to
use asciidoc {version} macro to avoid having to invoke sed.

Makefile

@@ -16,9 +16,10 @@ DOCS	= $(DOCS_MAN) $(DOCS_HTML) \
 	  manual.toc manual.pdf
 
 ifneq (,$(wildcard .git))
-VERSION = $(shell git-describe)
-WTDIRTY = $(shell git-diff-index --name-only HEAD 2>/dev/null)
-CFLAGS += '-DVERSION="$(VERSION)$(if $(WTDIRTY),-dirty)"'
+GITDESC = $(subst tig-,,$(shell git describe))
+WTDIRTY = $(if $(shell git-diff-index HEAD 2>/dev/null),-dirty)
+VERSION = $(GITDESC)$(WTDIRTY)
+CFLAGS += '-DVERSION="tig-$(VERSION)"'
 endif
 
 all: $(PROGS)
@@ -88,7 +89,7 @@ README.html: README
 	asciidoc -b xhtml11 -d manpage $<
 
 %.1.xml : %.1.txt
-	asciidoc -b docbook -d manpage $<
+	asciidoc -b docbook -d manpage -aversion=$(VERSION) $<
 
 %.1 : %.1.xml
 	xmlto -m manpage.xsl man $<
@@ -97,7 +98,7 @@ README.html: README
 	asciidoc -b xhtml11 -d manpage $<
 
 %.5.xml : %.5.txt
-	asciidoc -b docbook -d manpage $<
+	asciidoc -b docbook -d manpage -aversion=$(VERSION) $<
 
 %.5 : %.5.xml
 	xmlto -m manpage.xsl man $<

asciidoc.conf

@@ -21,6 +21,25 @@ ifdef::backend-xhtml11[]
 <a href="{target}{0?.{0}}.html">{target}{0?({0})}</a>
 endif::backend-xhtml11[]
 
+ifdef::doctype-manpage[]
+ifdef::backend-docbook[]
+[header]
+template::[header-declarations]
+<refentry>
+<refmeta>
+<refentrytitle>{mantitle}</refentrytitle>
+<manvolnum>{manvolnum}</manvolnum>
+<refmiscinfo class="source">Tig</refmiscinfo>
+<refmiscinfo class="version">{version}</refmiscinfo>
+<refmiscinfo class="manual">Tig Manual</refmiscinfo>
+</refmeta>
+<refnamediv>
+  <refname>{manname}</refname>
+  <refpurpose>{manpurpose}</refpurpose>
+</refnamediv>
+endif::backend-docbook[]
+endif::doctype-manpage[]
+
 ifdef::readme[]
 # No header or footers for README.html
 [header]