Document COMMON_GIT_*

playbooks/roles/common/defaults/main.yml

@@ -30,10 +30,13 @@ COMMON_DEPLOYMENT: 'default_deployment'
 COMMON_PYPI_MIRROR_URL: 'https://pypi.python.org/simple'
 COMMON_NPM_MIRROR_URL: 'http://registry.npmjs.org'
 COMMON_UBUNTU_APT_KEYSERVER: "http://keyserver.ubuntu.com/pks/lookup?op=get&fingerprint=on&search="
-# do not include http/https
-COMMON_GIT_PROTOCOL: 'https'
-COMMON_GIT_MIRROR: 'github.com'
-COMMON_GIT_PATH: 'edx'
+
+#The git checkout url in most roles is constructed from these values
+#e.g. https://{{COMMON_GIT_MIRROR}}/{{COMMON_GIT_PATH}}/repo.git
+COMMON_GIT_PROTOCOL: 'https'  # https|ssh
+COMMON_GIT_MIRROR: 'github.com' # git server hostname
+COMMON_GIT_PATH: 'edx'  # git path prefix
+
 # override this var to set a different hostname
 COMMON_HOSTNAME: ""