standardize upstream version-check comments across roles

Reword and reposition the lookup comment above each upstream _version
var to a single greppable "# version-check: <url>" marker, matching the
convention adopted in ansible-roles: always directly above the version
line, one grep finds every instance.

Covers bitcoind, bitcoind-prometheus-exporter, lnd (lnd_version and
lndconnect_version, the latter had no lookup comment before), and
lnurld/build, which points at the upstream commits page since
lnurld_version pins a commit hash rather than a release tag.

Document the convention in the README.

1 files changed, 17 insertions, 0 deletions

diff --git a/README.md b/README.md
index 17befca..007b0e0 100644
--- a/README.md
+++ b/README.md
@@ -3,3 +3,20 @@
 https://src.nth.io/bitcoin-ansible-roles/file
 
 bitcoind node without a wallet with an lnd node with wallet.
+
+## Dependency Version Checks
+
+Roles that pin an upstream dependency's version carry a comment directly above the `_version`
+variable in `defaults/main.yaml`, pointing at the page where the current upstream version can be
+confirmed:
+
+```yaml
+# version-check: https://github.com/lightningnetwork/lnd/releases
+lnd_version: "0.20.2-beta"
+```
+
+Find every instance across the repo with:
+
+```sh
+grep -rn "# version-check:" --include="*.yaml" .
+```