config.txt: refer to --upload-pack and --receive-pack instead of --exec

The options --upload-pack (of git-fetch-pack) and --receive-pack (of
git-push) do the same as --exec (for both commands).  But the former options
have the more descriptive name.

Signed-off-by: Uwe Kleine-König <Uwe.Kleine-Koenig@digi.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -796,15 +796,15 @@ remote.<name>.skipDefaultUpdate::
 
 remote.<name>.receivepack::
 	The default program to execute on the remote side when pushing.  See
-	option \--exec of linkgit:git-push[1].
+	option \--receive-pack of linkgit:git-push[1].
 
 remote.<name>.uploadpack::
 	The default program to execute on the remote side when fetching.  See
-	option \--exec of linkgit:git-fetch-pack[1].
+	option \--upload-pack of linkgit:git-fetch-pack[1].
 
 remote.<name>.tagopt::
-	Setting this value to --no-tags disables automatic tag following when fetching
-	from remote <name>
+	Setting this value to \--no-tags disables automatic tag following when
+	fetching from remote <name>
 
 remotes.<group>::
 	The list of remotes which are fetched by "git remote update