admin: Fix check if PR or release branch docs build

Uses built-in RTD vars.  https://docs.readthedocs.io/en/stable/environment-variables.html.

Follow up to https://github.com/ceph/ceph/pull/46917#discussion_r942359130.

Signed-off-by: David Galloway <dgallowa@redhat.com>

diff --git a/admin/rtd-checkout-main b/admin/rtd-checkout-main
index 931816dce9ed53035a48575e47a7e619cd08c7b4..829d7c384699137ec64e9da45f0f3732e7a4de69 100755 (executable)
--- a/admin/rtd-checkout-main
+++ b/admin/rtd-checkout-main
@@ -1,6 +1,10 @@
 # See .readthedocs.yml
 set -ex
-if git symbolic-ref HEAD; then
+re='^[0-9]+$'
+if [[ $READTHEDOCS_VERSION =~ $re ]]; then
+  echo "Building docs for PR $READTHEDOCS_VERSION.  Will not check out doc/releases from main branch."
+else
+  echo "Building docs for $READTHEDOCS_VERSION branch.  Will check out doc/releases from main branch."
   git checkout origin/main -- doc/releases
 fi
 git status