Add Abstract: support for howto index generator.

Maybe it's time for me to really learn asciidoc.  Also I should do Perl ;-).

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/howto-index.sh

@@ -20,8 +20,30 @@ do
 		s/[ 	]*$//
 		s/^/by /
 		p
+	}
+	' "$txt"`
+
+	abstract=`sed -ne '
+	/^Abstract:[ 	]/{
+		s/^[^ 	]*//
+		x
+		s/.*//
+		x
+		: again
+		/^[ 	]/{
+			s/^[ 	]*//
+			H
+			n
+			b again
+		}
+		x
+		p
+		q
 	}' "$txt"`
-	echo "
+
-	* link:$txt[$title] $from"
+	echo "* link:$txt[$title] $from
+$abstract
+
+"
 
 done

Documentation/howto/make-dist.txt

@@ -3,6 +3,11 @@ From: Linus Torvalds <torvalds@osdl.org>
 To: Dave Jones <davej@redhat.com>
 cc: git@vger.kernel.org
 Subject: Re: Fwd: Re: git checkout -f branch doesn't remove extra files
+Abstract: In this article, Linus talks about building a tarball,
+ incremental patch, and ChangeLog, given a base release and two
+ rc releases, following the convention of giving the patch from
+ the base release and the latest rc, with ChangeLog between the
+ last rc and the latest rc.
 
 On Sat, 13 Aug 2005, Dave Jones wrote:
 >

Documentation/howto/rebase-and-edit.txt

@@ -3,6 +3,9 @@ From:	Linus Torvalds <torvalds@osdl.org>
 To:	Steve French <smfrench@austin.rr.com>
 cc:	git@vger.kernel.org
 Subject: Re: sending changesets from the middle of a git tree
+Abstract: In this article, Linus demonstrates how a broken commit
+ in a sequence of commits can be removed by rewinding the head and
+ reapplying selected changes.
 
 On Sat, 13 Aug 2005, Linus Torvalds wrote:
 

Documentation/howto/rebase-from-internal-branch.txt

@@ -3,6 +3,11 @@ To:	git@vger.kernel.org
 Cc:	Petr Baudis <pasky@suse.cz>, Linus Torvalds <torvalds@osdl.org>
 Subject: Re: sending changesets from the middle of a git tree
 Date:	Sun, 14 Aug 2005 18:37:39 -0700
+Abstract: In this article, JC talks about how he rebases the
+ public "pu" branch using the core GIT tools when he updates
+ the "master" branch, and how "rebase" works.  Also discussed
+ is how this applies to individual developers who sends patches
+ upstream.
 
 Petr Baudis <pasky@suse.cz> writes:
 

Documentation/howto/using-topic-branches.txt

@@ -1,6 +1,8 @@
 Date: Mon, 15 Aug 2005 12:17:41 -0700
 From: tony.luck@intel.com
 Subject: Some tutorial text (was git/cogito workshop/bof at linuxconf au?)
+Abstract: In this article, Tony Luck discusses how he uses GIT
+ as a Linux subsystem maintainer.
 
 Here's something that I've been putting together on how I'm using
 GIT as a Linux subsystem maintainer.