* 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.
Before that, 'guix environment guile' (for instance) would define environment
variables that would refer to the "include" output of Bash, the "debug" output
of libgc, etc., even though these are not listed as inputs in the recipe of
'guile'.
* guix/gexp.scm (lower-inputs): Export.
* guix/scripts/environment.scm (evaluate-input-search-paths): Remove
'derivations' parameter; add 'search-paths'. Expect 'inputs' to be
a list of tuples. Adjust callers.
(create-environment): Remove 'derivations' parameter; add 'search-paths'.
(show-search-paths): Likewise.
(package+propagated-inputs): New procedure.
(packages->transitive-inputs, packages+propagated-inputs): Remove.
(build-inputs): Expect INPUTS to be a list of derivation tuples.
(guix-environment): Compute INPUTS using 'package+propagated-inputs',
'package->bag', and 'bag-transitive-inputs'. Move 'run-with-store' higher.
* tests/guix-environment.sh: Add test with FINDUTILS-BOOT0.
