git-archive: update documentation

This patch documents zip backend options.

It also adds git-archive command into the main git manual
page.
Signed-off-by: NFranck Bui-Huu <vagabon.xyz@gmail.com>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

Documentation/git-archive.txt

@@ -40,6 +40,7 @@ OPTIONS
 
 <extra>::
 	This can be any options that the archiver backend understand.
+	See next section.
 
 --remote=<repo>::
 	Instead of making a tar archive from local repository,
@@ -52,6 +53,18 @@ path::
 	If one or more paths are specified, include only these in the
 	archive, otherwise include all files and subdirectories.
 
+BACKEND EXTRA OPTIONS
+---------------------
+
+zip
+~~~
+-0::
+	Store the files instead of deflating them.
+-9::
+	Highest and slowest compression level.  You can specify any
+	number from 1 to 9 to adjust compression speed and ratio.
+
+
 CONFIGURATION
 -------------
 By default, file and directories modes are set to 0666 or 0777 in tar

Documentation/git.txt

@@ -266,6 +266,9 @@ gitlink:git-am[1]::
 gitlink:git-applymbox[1]::
 	Apply patches from a mailbox, original version by Linus.
 
+gitlink:git-archive[1]::
+	Creates an archive of files from a named tree.
+
 gitlink:git-bisect[1]::
 	Find the change that introduced a bug by binary search.