Commit eee95b5a87 changed package
rewriting to ignore hidden packages. This patch permits the previous use
by adding an option to rewrite hidden packages.
* guix/packages.scm (package-input-rewriting/spec)[rewrite]: When P is
hidden, return it as-is unless #:replace-hidden? has been enabled.
* tests/packages.scm ("package-input-rewriting/spec, replace hidden
package"): New test.
* doc/guix.texi (Defining Package Variants): Update.
Change-Id: I0a7988cac70e0c6b88b0fe6e27c1036fa723e030
Signed-off-by: Ludovic Courtès <ludo@gnu.org>