main: Start command line option parsing

Include the 'unix-opts' library described in
http://lispcookbook.github.io/cl-cookbook/scripting.html#parsing-command-line-arguments
for command line option parsing.

Define the options I need. We want a `--socket-url` option, and a list
of extension IDs as free arguments.

Implement the `-V` version command line argument. Thanks to JJJ
(https://stackoverflow.com/users/1337941/jjj) on Stack Overflow for
describing how to get the version number of an ASDF system:
https://stackoverflow.com/questions/11084339/getting-the-version-of-an-asdf-system/11088022#11088022

Add a new `options.lisp` file where we'll add the option parsing restart
error handling functions required by 'unix-opts'.

1 files changed, 6 insertions, 0 deletions

diff --git a/l/src/option.lisp b/l/src/option.lisp
new file mode 100644
index 0000000..d828230
--- /dev/null
+++ b/l/src/option.lisp
@@ -0,0 +1,6 @@
+(in-package :extreload)
+
+(defmacro when-option ((options option) &body body)
+  `(let ((value (getf ,options ,option)))
+     (when value
+       ,@body)))