Add --show option to build-dir command

The new option shows the current build directory, if present.

build/_build-dir

@@ -1,6 +1,7 @@
 #compdef build-dir
 
 _arguments \
-  '(-h --help)'{-h,--help}'[]' \
+  '(-h --help)'{-h,--help}'[show this help message and exit]' \
+  '(-s --show)'{-s,--show}'[show the current build directory]' \
   '--build[invoke a build after selection]' \
   '1:directory:_files'

build/build.plugin.zsh

@@ -32,8 +32,8 @@ fi
 # Interactively choose a `~build` directory for `build` to build.
 build-dir() {
   local usage='usage: build-dir [-h] [--build] [<directory>]'
-  local -a help do_build
-  zparseopts -D h=help -help=help -build=do_build
+  local -a help show do_build
+  zparseopts -D h=help -help=help s=show -show=show -build=do_build
   if [[ -n $help ]]; then
     cat << EOF
 $usage
@@ -45,12 +45,22 @@ positional arguments:
 
 optional arguments:
   -h, --help  show this help message and exit
+  -s, --show  show the current build directory
   --build     invoke a build after selection
 EOF
     return
   fi
   error() { echo "\e[31merror:\e[0m $1" }
   warning() { echo "\e[33mwarning:\e[0m $1" }
+  if [[ -n $show ]]; then
+    if [[ ! -n $build_dir ]]; then
+      error "build directory not set"
+      return 1
+    else
+      echo "$build_dir"
+      return
+    fi
+  fi
   local local_build_dir
   if [[ ${#*} -gt 1 ]]; then
     echo $usage