Allow empty string as flag argument

lib/bashly/views/flag/case.erb

@@ -1,7 +1,7 @@
 # :flag.case
 <%= aliases.join " | " %> )
 % if arg
-  if [[ $2 ]]; then
+  if [[ -n ${2+x} ]]; then
     args[<%= name %>]="$2"
     shift
     shift

spec/approvals/examples/empty-args

@@ -0,0 +1,17 @@
+creating user files in src
+skipped src/initialize.sh (exists)
+skipped src/test_command.sh (exists)
+created ./cli
+run ./cli --help to test your bash script
++ ./cli test ''
+# this file is located in 'src/test_command.sh'
+# code for 'cli test' goes here
+# you can edit it freely and regenerate (it will not be overwritten)
+args:
+- ${args[arg]} = 
++ ./cli test --flag ''
+# this file is located in 'src/test_command.sh'
+# code for 'cli test' goes here
+# you can edit it freely and regenerate (it will not be overwritten)
+args:
+- ${args[--flag]} = 

spec/fixtures/workspaces/empty-args/.gitignore

@@ -0,0 +1 @@
+cli

spec/fixtures/workspaces/empty-args/src/bashly.yml

@@ -0,0 +1,12 @@
+name: cli
+help: Sample application
+version: 0.1.0
+
+commands:
+- name: test
+  help: Run test
+  flags:
+  - long: --flag
+    arg: value
+  args:
+  - name: arg

spec/fixtures/workspaces/empty-args/src/initialize.sh

@@ -0,0 +1,6 @@
+# Code here runs inside the initialize() function
+# Use it for anything that you need to run before any other function, like
+# setting environment vairables:
+# CONFIG_FILE=settings.ini
+#
+# Feel free to empty (but not delete) this file.

spec/fixtures/workspaces/empty-args/src/test_command.sh

@@ -0,0 +1,4 @@
+echo "# this file is located in 'src/test_command.sh'"
+echo "# code for 'cli test' goes here"
+echo "# you can edit it freely and regenerate (it will not be overwritten)"
+inspect_args

spec/fixtures/workspaces/empty-args/test.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+# This fixture tests Bash 4+-only syntax
+# It is executed as part of the Runfile examples test
+
+bundle exec bashly generate
+
+set -x
+
+./cli test ''
+./cli test --flag ''

spec/fixtures/workspaces/flag-args-with-dash/argflag

@@ -142,7 +142,7 @@ parse_requirements() {
 
     # :flag.case
     --options | -o )
-      if [[ $2 ]]; then
+      if [[ -n ${2+x} ]]; then
         args[--options]="$2"
         shift
         shift