user-manual: improve html and pdf formatting

Use asciidoc style 'article' instead of 'book' and change asciidoc
title level.  This removes blank first page and superfluous "Part I"
page (there is no "Part II") in pdf output. Also pdf size is
decreased by this from 77 to 67 pages.  In html output this removes
unnecessary sub-tocs and chapter numbering.

Signed-off-by: Thomas Ackermann <th.acker@arcor.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/Makefile

@@ -324,7 +324,7 @@ manpage-base-url.xsl: manpage-base-url.xsl.in
 
 user-manual.xml: user-manual.txt user-manual.conf
 	$(QUIET_ASCIIDOC)$(RM) $@+ $@ && \
-	$(ASCIIDOC) $(ASCIIDOC_EXTRA) -b docbook -d book -o $@+ $< && \
+	$(ASCIIDOC) $(ASCIIDOC_EXTRA) -b docbook -d article -o $@+ $< && \
 	mv $@+ $@
 
 technical/api-index.txt: technical/api-index-skel.txt \

Documentation/user-manual.txt

@@ -1,5 +1,5 @@
 Git User Manual
-_______________
+===============
 
 Git is a fast distributed revision control system.