ledger: correct the CHECK PASS message to name the pinned revision

wizard-work/ledger/verify_commits_check.py

@@ -136,12 +136,10 @@ def main():
         for f in failures:
             print(" -", f)
         return 1
-    head = git("rev-parse", "--short=7", "HEAD").strip()
     print(
-        "CHECK PASS | re-derived {0} commits from git HEAD {1}; commits.tsv/json/detail.tsv/md "
-        "byte-identical to git-derived bytes; Files column = true changed-path count".format(
-            len(rows), head
-        )
+        "CHECK PASS | re-derived %d commits from pinned revision %s (git log -n 20 %s); commits.tsv/json/detail.tsv/md "
+        "byte-identical to git-derived bytes; Files column = true changed-path count"
+        % (len(rows), PINNED_REV, PINNED_REV)
     )
     return 0