separate tar.* config to its own source file

Even though there is only one configuration variable in the
namespace, it is not quite right to have tar.umask described
among the variables for tag.* namespace.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -445,6 +445,8 @@ include::config/submodule.txt[]
 
 include::config/tag.txt[]
 
+include::config/tar.txt[]
+
 include::config/trace2.txt[]
 
 include::config/transfer.txt[]

Documentation/config/tag.txt

@@ -15,10 +15,3 @@ tag.gpgSign::
 	convenient to use an agent to avoid typing your gpg passphrase
 	several times. Note that this option doesn't affect tag signing
 	behavior enabled by "-u <keyid>" or "--local-user=<keyid>" options.
-
-tar.umask::
-	This variable can be used to restrict the permission bits of
-	tar archive entries.  The default is 0002, which turns off the
-	world write bit.  The special value "user" indicates that the
-	archiving user's umask will be used instead.  See umask(2) and
-	linkgit:git-archive[1].

Documentation/config/tar.txt

@@ -0,0 +1,6 @@
+tar.umask::
+	This variable can be used to restrict the permission bits of
+	tar archive entries.  The default is 0002, which turns off the
+	world write bit.  The special value "user" indicates that the
+	archiving user's umask will be used instead.  See umask(2) and
+	linkgit:git-archive[1].