Manual.md: document renaming a package

Manual.md

@@ -42,6 +42,7 @@ packages for XBPS, the `Void Linux` native packaging system.
 	* [Go packages](#pkgs_go)
 	* [Haskell packages](#pkgs_haskell)
 	* [Font packages](#pkgs_font)
+	* [Renaming a package](#pkg_rename)
 	* [Removing a package](#pkg_remove)
 	* [XBPS Triggers](#xbps_triggers)
 		* [appstream-cache](#triggers_appstream_cache)
@@ -1659,6 +1660,18 @@ cache during the install/removal of the package
 - `font_dirs`: which should be set to the directory where the package
 installs its fonts
 
+<a id="pkg_rename"></a>
+### Renaming a package
+
+- Create empty package of old name, depending on new package. This is
+necessary to provide updates to systems where old package is already
+installed. This should be a subpackage of new one, except when version
+number of new package decreased: then create a separate template using
+old version and increased revision.
+- Edit references to package in other templates and common/shlibs.
+- Don't set `replaces=`, it can result in removing both packages from
+systems by xbps.
+
 <a id="pkg_remove"></a>
 ### Removing a package