Enable to pin a specific version of pyenv.

This PR is an updated version of avanov#54.

credits to @BielStela

Closes avanov#54

defaults/main.yml

@@ -19,6 +19,10 @@ pyenv_update: no
 pyenv_python_configure_opts: ""
 pyenv_uninstall_python_w_wrong_configure_opts: no
 
+# aditional option to pin the pyenv and pyenv-virtualenv version
+pyenv_git_ref: ""
+pyenv_virtualenv_git_ref: ""
+
 pyenv_debian_packages:
   - build-essential
   # On Ubuntu 12.04 build may fail with the following error:

tasks/install.yml

@@ -1,15 +1,31 @@
 ---
+- name: Install PyEnv from git ref
+  git:
+    repo: https://github.com/pyenv/pyenv.git
+    dest: "{{ pyenv_path }}"
+    version: "{{ pyenv_git_ref }}"
+  when: pyenv_git_ref
+
 - name: Install PyEnv
   git:
     repo: https://github.com/pyenv/pyenv.git
     dest: "{{ pyenv_path }}"
     update: "{{ pyenv_update_git_install }}"
+  when: pyenv_git_ref is undefined
+
+- name: Install PyEnv-virtualenv plugin from git ref
+  git:
+    repo: https://github.com/yyuu/pyenv-virtualenv.git
+    dest: "{{ pyenv_path }}/plugins/pyenv-virtualenv"
+    version: "{{ pyenv_virtualenv_git_ref }}"
+  when: pyenv_virtualenv_git_ref
 
 - name: Install PyEnv-virtualenv plugin
   git:
     repo: https://github.com/yyuu/pyenv-virtualenv.git
     dest: "{{ pyenv_path }}/plugins/pyenv-virtualenv"
     update: "{{ pyenv_update_git_install }}"
+  when: pyenv_virtualenv_git_ref is undefined
 
 - name: Install PyEnv-update plugin
   git: