Add support for apk

Supports status, install, upgrade and delete actions.

Closes #103

test/fixtures/apk-version.txt

@@ -0,0 +1,3 @@
+Installed:                                Available:
+apk-tools-2.8.1-r1                      < 2.8.1-r2
+outdated_package-1.1.0-r1               < 1.2.0-r1

test/type-apk.bats

@@ -0,0 +1,57 @@
+#!/usr/bin/env bats
+
+. test/helpers.sh
+
+apk() { . $BORK_SOURCE_DIR/types/apk.sh "$@"; }
+
+@test "apk status returns FAILED_PRECONDITION when apk is missing" {
+  respond_to 'which apk' 'return 1'
+  run apk status something
+  echo "# status: ${status}"
+  echo '# output:'; echo "${output}" | sed -re 's/^/#   /'
+  (( status == STATUS_FAILED_PRECONDITION ))
+}
+
+@test "apk status returns MISSING when package is not installed" {
+  respond_to 'apk info --installed missing_package_is_missing' \
+    'return 1'
+
+  run apk status missing_package_is_missing
+  (( status == STATUS_MISSING ))
+}
+
+@test "apk status returns OK when packge is installed and current" {
+  respond_to 'apk info --installed current_package' \
+    'echo current_package'
+
+  run apk status current_package
+  (( status == STATUS_OK ))
+}
+
+@test "apk status returns OUTDATED when package is installed but outdated" {
+  respond_to "apk version" "cat ${fixtures}/apk-version.txt"
+
+  run apk status outdated_package
+  (( status == STATUS_OUTDATED ))
+}
+
+@test "apk install runs 'add pkg'" {
+  run apk install missing_package_is_missing
+  (( status == 0 ))
+  run baked_output
+  [[ ${output} == 'sudo apk add missing_package_is_missing' ]]
+}
+
+@test "apk upgrade runs 'add pkg'" {
+  run apk upgrade outdated_package
+  (( status == 0 ))
+  run baked_output
+  [[ ${output} == 'sudo apk add outdated_package' ]]
+}
+
+@test "apk delete runs 'del pkg'" {
+  run apk delete current_package
+  (( status == 0 ))
+  run baked_output
+  [[ ${output} == 'sudo apk del current_package' ]]
+}

types/apk.sh

@@ -0,0 +1,27 @@
+#!/bin/bash
+
+action=$1
+name=$2
+shift 2
+
+case "${action}" in
+  desc)
+    printf '%s\n' \
+      'asserts presence of packages installed via apk (Alpine Package Manager)' \
+      '* apk packge-name    (install/upgrade given package)'
+    ;;
+  status)
+    needs_exec "apk" || return "${STATUS_FAILED_PRECONDITION}"
+
+    bake apk info --installed "${name}" || return "${STATUS_MISSING}"
+    ! bake apk version | egrep "^${name}-\d" || return "${STATUS_OUTDATED}"
+    return "${STATUS_OK}"
+    ;;
+  install|upgrade)
+    bake sudo apk add "${name}"
+    ;;
+  delete)
+    bake sudo apk del "${name}"
+    ;;
+  *) return 1 ;;
+esac