Add a 'list' command to aikup.

aikup/aikup

@@ -17,6 +17,10 @@ main() {
       --)               shift; break;;
 
       install)     shift; AIKUP_VERSION=$1;;
+      -l|--list)
+	list_versions
+	exit 0
+	;;
       -h|--help)
         usage
         exit 0
@@ -116,6 +120,7 @@ USAGE:
     aikup <SUBCOMMAND>
 
 OPTIONS:
+    -l, --list      List available versions
     -h, --help      Print help information
 
 SUBCOMMANDS:
@@ -123,6 +128,11 @@ SUBCOMMANDS:
 EOF
 }
 
+list_versions() {
+  say "available versions"
+  curl -sSL "https://api.github.com/repos/aiken-lang/aiken/tags" | grep -E '"name": "v' | sed 's/.*\(v[^"]*\)",.*/\1/'
+}
+
 say() {
   printf "aikup: %s\n" "$1"
 }
@@ -157,21 +167,20 @@ ensure() {
 banner() {
   printf '
 
-.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx
+================================================================================
 
- ╔═╗ ╦ ╔╦ ║ ╔══ ╔╗╔           Modern and modular toolkit
+░█▀▀▄░▀█▀░▒█░▄▀░▒█▀▀▀░▒█▄░▒█             Modern and modular toolkit
- ╠═╣ ║  ╠═╣ ╠═  ║║║     for Cardano Smart Contract Development 
+▒█▄▄█░▒█░░▒█▀▄░░▒█▀▀▀░▒█▒█▒█       for Cardano Smart Contract development.
- ╚ ╝ ╩  ╚ ╚ ╚══ ╝╚╝               written in Rust.
+▒█░▒█░▄█▄░▒█░▒█░▒█▄▄▄░▒█░░▀█                 Written in Rust.
 
-.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx
+================================================================================
 
 Repo       : https://github.com/aiken-lang/aiken
 Docs       : https://aiken-lang.org/
 Chat       : https://discord.gg/Vc3x8N9nz2
 Contribute : https://github.com/aiken-lang/aiken/blob/main/CONTRIBUTING.md
 
-.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx.xOx
+================================================================================
-
 '
 }