pack: Wrapper honors 'GUIX_EXECUTION_ENGINE' environment variable.

* gnu/packages/aux-files/run-in-namespace.c (struct engine): New type.
(exec_default): New function.
(engines): New variable.
(execution_engine): New function.
(main): Use it instead of calling 'exec_in_user_namespace' and
'exec_with_proot' directly.
* tests/guix-pack-relocatable.sh: Add test with 'GUIX_EXECUTION_ENGINE'.
* doc/guix.texi (Invoking guix pack): Document 'GUIX_EXECUTION_ENGINE'.

1 files changed, 17 insertions, 0 deletions

diff --git a/tests/guix-pack-relocatable.sh b/tests/guix-pack-relocatable.sh
index a3fd45623c2..cb56815fed7 100644
--- a/tests/guix-pack-relocatable.sh
+++ b/tests/guix-pack-relocatable.sh
@@ -84,6 +84,23 @@ fi
 grep 'GNU sed' "$test_directory/output"
 chmod -Rf +w "$test_directory"; rm -rf "$test_directory"/*
 
+case "`uname -m`" in
+    x86_64|i?86)
+        # Try '-RR' and PRoot.
+        tarball="`guix pack -RR -S /Bin=bin sed`"
+        tar tvf "$tarball" | grep /bin/proot
+        (cd "$test_directory"; tar xvf "$tarball")
+        GUIX_EXECUTION_ENGINE="proot"
+        export GUIX_EXECUTION_ENGINE
+        "$test_directory/Bin/sed" --version > "$test_directory/output"
+        grep 'GNU sed' "$test_directory/output"
+        chmod -Rf +w "$test_directory"; rm -rf "$test_directory"/*
+        ;;
+    *)
+        echo "skipping PRoot test" >&2
+        ;;
+esac
+
 # Ensure '-R' works with outputs other than "out".
 tarball="`guix pack -R -S /share=share groff:doc`"
 (cd "$test_directory"; tar xvf "$tarball")