Use a git repository for installing plugins.

.gitignore

@@ -1,5 +1,5 @@
 installs
 plugins
 shims
+repository
 .vagrant
-

help.txt

@@ -1,5 +1,5 @@
 MANAGE PLUGINS
-  asdf plugin-add <name> <git-url>     Add git repo as plugin
+  asdf plugin-add <name> [<git-url>]   Add a plugin
   asdf plugin-list                     List installed plugins
   asdf plugin-remove <name>            Remove plugin and package versions
   asdf plugin-update <name>            Update plugin

lib/commands/plugin-add.sh

@@ -1,11 +1,23 @@
 plugin_add_command() {
-  if [ "$#" -ne 2 ]; then
-    display_error "usage: asdf plugin-add <name> <git-url>"
+  if [[ $# -lt 1 || $# -gt 2 ]]; then
+    display_error "usage: asdf plugin-add <name> [<git-url>]"
     exit 1
   fi
 
   local plugin_name=$1
-  local source_url=$2
+
+  if [ -n "$2" ]; then
+    local source_url=$2
+  else
+    initialize_or_update_repository
+    local source_url=$(get_plugin_source_url $plugin_name)
+  fi
+
+  if [ -z "$source_url" ]; then
+    display_error "plugin $plugin_name not found in repository"
+    exit 1
+  fi
+
   local plugin_path=$(get_plugin_path $plugin_name)
 
   mkdir -p $(asdf_dir)/plugins

lib/utils.sh

@@ -206,3 +206,29 @@ get_asdf_config_value() {
         get_asdf_config_value_from_file $default_config_path $key
     fi
 }
+
+asdf_repository_url() {
+  echo "https://github.com/doughsay/asdf-plugins.git"
+}
+
+initialize_or_update_repository() {
+  local repository_url=$(asdf_repository_url)
+  local repository_path=$(asdf_dir)/repository
+
+  if [ -d $repository_path ]; then
+    echo "updating plugin repository..."
+    (cd $repository_path && git pull)
+  else
+    echo "initializing plugin repository..."
+    git clone $repository_url $repository_path
+  fi
+}
+
+get_plugin_source_url() {
+  local plugin_name=$1
+  local plugin_config="$(asdf_dir)/repository/plugins/$plugin_name"
+
+  if [ -f $plugin_config ]; then
+    cat $plugin_config | grep "repository" | awk -F'=' '{print $2}' | sed 's/ //'
+  fi
+}