guix gc: Add `--references' and `--referrers'.

* guix/scripts/gc.scm (show-help): Update.
  (%options): Add `--references' and `--referrers'.
  (guix-gc)[symlink-target, store-directory]: New procedures.
  Handle the `list-references' and `list-referrers' actions.
* tests/guix-gc.sh: Add tests for `--references'.
* doc/guix.texi (Invoking guix gc): Document `--references' and
  `--referrers'.

1 files changed, 12 insertions, 0 deletions

diff --git a/tests/guix-gc.sh b/tests/guix-gc.sh
index a90d085ab2..eac9d82e89 100644
--- a/tests/guix-gc.sh
+++ b/tests/guix-gc.sh
@@ -25,6 +25,18 @@ guix gc --version
 trap "rm -f guix-gc-root" EXIT
 rm -f guix-gc-root
 
+# Check the references of a .drv.
+drv="`guix build guile-bootstrap -d`"
+out="`guix build guile-bootstrap`"
+test -f "$drv" && test -d "$out"
+
+guix gc --references "$drv" | grep -e -bash
+guix gc --references "$out"
+guix gc --references "$out/bin/guile"
+
+if guix gc --references /dev/null;
+then false; else true; fi
+
 # Add then reclaim a .drv file.
 drv="`guix build idutils -d`"
 test -f "$drv"