environment: For --ad-hoc, allow users to specify an output.

* guix/scripts/environment.scm (package+propagated-inputs): Add 'output'
  parameter.  Use it in return value.
  (options/resolve-packages): Use 'append-map' instead of 'map'.  For 'load'
  and 'expression', return all the outputs of the resulting package.  For
  'package', use 'specification->package+output' instead of
  'specification->package'.
  (guix-environment): Adjust uses of PACKAGES accordingly.
* doc/guix.texi (Invoking guix environment): Document it.
* tests/guix-environment.sh: Add test for --ad-hoc guile-bootstrap:out.

1 files changed, 5 insertions, 0 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 71167dfdc7..119c2d9c98 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -4211,6 +4211,11 @@ guix environment --ad-hoc guile guile-sdl -E guile
 runs @command{guile} in an environment where Guile and Guile-SDL are
 available.
 
+Note that this example implicitly asks for the default output of
+@code{guile} and @code{guile-sdl} but it is possible to ask for a
+specific output---e.g., @code{glib:bin} asks for the @code{bin} output
+of @code{glib} (@pxref{Packages with Multiple Outputs}).
+
 @item --pure
 Unset existing environment variables when building the new environment.
 This has the effect of creating an environment in which search paths