add gentoo package testing script

.local/bin/chroot_testing

@@ -0,0 +1,53 @@
+#!/bin/zsh
+# chroot into an environment for gentoo package testing
+# no argument: modify template
+# first argument: suffix of the test subvolume
+
+setopt LOCAL_OPTIONS ERR_RETURN NO_UNSET PIPE_FAIL
+
+local chroot_dir="/mnt/testing"
+
+if [[ "$(id -u)" != 0 ]]; then
+    print -Pu2 "%B%F{red}you have to be root%f%b"
+    return 1
+fi
+
+if [[ -v 1 ]]; then
+    chroot_dir="${chroot_dir}_${1}"
+    if [[ ! -d ${chroot_dir} ]]; then
+        btrfs subvolume snapshot /mnt/testing "${chroot_dir}"
+    fi
+fi
+
+cp --dereference /etc/resolv.conf ${chroot_dir}/etc/
+
+mount --types proc /proc ${chroot_dir}/proc
+mount --rbind /sys ${chroot_dir}/sys
+mount --rbind /dev ${chroot_dir}/dev
+mount --rbind /run ${chroot_dir}/run
+
+mount -o bind,ro ~tea/src/gentoo ${chroot_dir}/var/db/repos/gentoo
+mount -o bind,ro ~tea/src/guru ${chroot_dir}/var/db/repos/guru
+
+chroot ${chroot_dir} /bin/bash -l
+
+function _try_umount() {
+    local dir=${1}
+
+    setopt NO_ERR_RETURN
+    umount --recursive ${dir} || umount --lazy ${dir}
+    setopt ERR_RETURN
+}
+
+_try_umount ${chroot_dir}/var/db/repos/guru
+_try_umount ${chroot_dir}/var/db/repos/gentoo
+
+_try_umount ${chroot_dir}/run
+_try_umount ${chroot_dir}/dev
+_try_umount ${chroot_dir}/sys
+_try_umount ${chroot_dir}/proc
+
+if [[ -v 1 ]]; then
+    print -Pu2 "%F{blue}delete snapshot with%f" \
+        "%F{magenta}btrfs subvolume delete ${chroot_dir}%f"
+fi