Use a git repository for installing plugins.

.gitignore

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

README.md

@@ -49,7 +49,7 @@ mkdir -p ~/.config/fish/completions; and cp ~/.asdf/completions/asdf.fish ~/.con
 Plugins are how asdf understands how to handle different packages. Below is a list of plugins for languages. There is a [super-simple API](https://github.com/asdf-vm/asdf/blob/master/docs/creating-plugins.md) for supporting more languages.
 
 | Language  | Repository  | CI Status
-|-----------|-------------|---------- 
+|-----------|-------------|----------
 | Clojure   | [vic/asdf-clojure](https://github.com/vic/asdf-clojure) | [![Build Status](https://travis-ci.org/vic/asdf-clojure.svg?branch=master)](https://travis-ci.org/vic/asdf-clojure)
 | Crystal   | [marciogm/asdf-crystal](https://github.com/marciogm/asdf-crystal) | [![Build Status](https://travis-ci.org/marciogm/asdf-crystal.svg?branch=master)](https://travis-ci.org/marciogm/asdf-crystal)
 | D (DMD)   | [sylph01/asdf-dmd](https://github.com/sylph01/asdf-dmd) | [![Build Status](https://travis-ci.org/sylph01/asdf-dmd.svg?branch=master)](https://travis-ci.org/sylph01/asdf-dmd)
@@ -82,9 +82,16 @@ Plugins are how asdf understands how to handle different packages. Below is a li
 
 ##### Add a plugin
 
+```bash
+asdf plugin-add <name>
+# asdf plugin-add erlang
+```
+
+If the plugin you want to install is not part of the official plugins list, you can add it using its repository URL:
+
 ```bash
 asdf plugin-add <name> <git-url>
-# asdf plugin-add erlang https://github.com/asdf-vm/asdf-erlang.git
+# asdf plugin-add elm https://github.com/vic/asdf-elm
 ```
 
 ##### List installed plugins

docs/creating-plugins.md

@@ -117,3 +117,11 @@ os:
   - linux
   - osx
 ```
+
+## Submitting plugins to the official plugins repository
+
+`asdf` can easily install plugins by specifying the plugin repository url, e.g. `plugin-add my-plugin https://github.com/user/asdf-my-plugin.git`.
+
+To make it easier on your users, you can add your plugin to the official plugins repository to have your plugin listed and easily installable using a shorter command, e.g. `asdf plugin-add my-plugin`.
+
+Follow the instruction at the plugins repository: [asdf-vm/asdf-plugins](https://github.com/asdf-vm/asdf-plugins).

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 +1,24 @@
 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=$2
+  else
+    initialize_or_update_repository
+    local source_url
+    source_url=$(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 +206,35 @@ get_asdf_config_value() {
         get_asdf_config_value_from_file $default_config_path $key
     fi
 }
+
+asdf_repository_url() {
+  echo "https://github.com/asdf-vm/asdf-plugins.git"
+}
+
+initialize_or_update_repository() {
+  local repository_url
+  local repository_path
+
+  repository_url=$(asdf_repository_url)
+  repository_path=$(asdf_dir)/repository
+
+  if [ -d "$repository_path" ]; then
+    echo "updating plugin repository..."
+    (cd "$repository_path" && git fetch && git reset --hard origin/master)
+  else
+    echo "initializing plugin repository..."
+    git clone "$repository_url" "$repository_path"
+  fi
+}
+
+get_plugin_source_url() {
+  local plugin_name=$1
+  local plugin_config
+
+  plugin_config="$(asdf_dir)/repository/plugins/$plugin_name"
+
+
+  if [ -f "$plugin_config" ]; then
+    grep "repository" "$plugin_config" | awk -F'=' '{print $2}' | sed 's/ //'
+  fi
+}

test/plugin_commands.bats

@@ -0,0 +1,28 @@
+#!/usr/bin/env bats
+
+load test_helpers
+
+. $(dirname $BATS_TEST_DIRNAME)/lib/commands/plugin-add.sh
+. $(dirname $BATS_TEST_DIRNAME)/lib/commands/plugin-list.sh
+
+setup() {
+  setup_asdf_dir
+}
+
+teardown() {
+  clean_asdf_dir
+}
+
+@test "plugin_add command with no URL specified adds a plugin using repo" {
+  run plugin_add_command "elixir"
+  [ "$status" -eq 0 ]
+
+  run plugin_list_command
+  [ "$output" = "elixir" ]
+}
+
+@test "plugin_add command with no URL specified fails if the plugin doesn't exist" {
+  run plugin_add_command "does-not-exist"
+  [ "$status" -eq 1 ]
+  echo "$output" | grep "plugin does-not-exist not found in repository"
+}