Add shellcheck app management file

- See #3.

lib/sdd/apps/user/shellcheck

@@ -0,0 +1,23 @@
+#! /bin/bash
+
+sdd_install() {
+    local version=$1
+    local package=shellcheck-$version
+    local archive=$package.linux.x86_64.tar.xz
+
+    wget -P /tmp https://shellcheck.storage.googleapis.com/$archive
+    cd /tmp
+    tar xf $archive
+
+    mv $package/shellcheck "$SDD_INSTALL_PREFIX"/bin
+
+    rm -rf $archive $package
+}
+
+sdd_uninstall() {
+    rm -v "$SDD_INSTALL_PREFIX"/bin/shellcheck
+}
+
+sdd_fetch_latest_version() {
+    _name_of_latest_github_tag koalaman shellcheck
+}

test/apps/shellcheck.bats

@@ -0,0 +1,19 @@
+load '/usr/local/libexec/bats-support/load.bash'
+load '/usr/local/libexec/bats-assert/load.bash'
+
+@test "shellcheck of recent version can be installed and uninstalled" {
+  run sdd install shellcheck
+  assert_success
+  assert_line -n 0 -p 'Latest version available: '
+  assert_output -p 'Installed "shellcheck".'
+
+  run shellcheck --version
+  [ $status -eq 0 ]
+
+  run sdd uninstall shellcheck
+  [ $status -eq 0 ]
+  [ "${lines[-1]}" = 'Uninstalled "shellcheck".' ]
+
+  run which shellcheck
+  [ $status -eq 1 ]
+}