graph: Support package transformation options.

* guix/scripts/graph.scm (%options): Append %TRANSFORMATION-OPTIONS.
(show-help): Call 'show-transformation-options-help'.
(guix-graph): Call 'options->transformation' and use it.
* tests/guix-graph.sh: Add test.
* doc/guix.texi (Invoking guix graph): Document it.

1 files changed, 11 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 3a9d206b9f..3b8e5935bb 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -9907,7 +9907,18 @@ The package dependency graph is largely architecture-independent, but there
 are some architecture-dependent bits that this option allows you to visualize.
 @end table
 
+On top of that, @command{guix graph} supports all the usual package
+transformation options (@pxref{Package Transformation Options}).  This
+makes it easy to view the effect of a graph-rewriting transformation
+such as @option{--with-input}.  For example, the command below outputs
+the graph of @code{git} once @code{openssl} has been replaced by
+@code{libressl} everywhere in the graph:
 
+@example
+guix graph git --with-input=openssl=libressl
+@end example
+
+So many possibilities, so much fun!
 
 @node Invoking guix publish
 @section Invoking @command{guix publish}