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-rw-r--r--doc/guix.texi14
1 files changed, 14 insertions, 0 deletions
diff --git a/doc/guix.texi b/doc/guix.texi
index bf9dbaa726..a212666af0 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -1685,6 +1685,20 @@ of packages:
(list guile-2.0 "debug")))
@end example
+@findex specification->package+output
+In this example we have to know which modules define the @code{emacs}
+and @code{guile-2.0} variables to provide the right
+@code{use-package-modules} line, which can be cumbersome. We can
+instead provide regular package specifications and let
+@code{specification->package-output} look up the corresponding package
+objects, like this:
+
+@example
+(packages->manifest
+ (map (compose list specification->package+output)
+ '("emacs" "guile@@2.0" "guile@@2.0:debug")))
+@end example
+
@item --roll-back
@cindex rolling back
@cindex undoing transactions