Properly handle deleting commits that occur on multiple branches

guix-data-service/data-deletion.scm

@@ -146,7 +146,7 @@ AND id NOT IN (
       (delete-unreferenced-lint-checkers))))
 
 (define (delete-revisions-from-branch conn git-repository-id branch-name commits)
-  (define (delete-jobs conn)
+  (define (delete-jobs conn commits)
     (for-each
      (lambda (table)
        (exec-query
@@ -217,9 +217,7 @@ WHERE id IN (
           'delete-revisions-from-branch)
 
          (exec-query conn "SET LOCAL lock_timeout = '5s';")
-
          (delete-from-git-commits conn)
-         (delete-jobs conn)
 
          (let ((git-branch-id
                 (git-branch-for-repository-and-name conn
@@ -232,7 +230,25 @@ WHERE id IN (
 DROP TABLE IF EXISTS package_derivations_by_guix_revision_range_git_branch_"
              (number->string git-branch-id) ";")))
 
-         (delete-guix-revisions conn git-repository-id commits))))
+         (let ((now-unreferenced-commits
+                (filter
+                 (lambda (commit)
+                   (let ((result
+                          (null?
+                           (exec-query
+                            conn
+                            "SELECT 1 FROM git_commits WHERE commit = $1"
+                            commit))))
+                     (unless result
+                       (simple-format (current-error-port)
+                                      "skipping ~A because it's still referenced\n"
+                                      commit))
+                     result))
+                 commits)))
+           (delete-jobs conn now-unreferenced-commits)
+           (delete-guix-revisions conn
+                                  git-repository-id
+                                  now-unreferenced-commits)))))
     (lambda (key . args)
       (simple-format
        (current-error-port)