[ostree] repo: create a tombstone commit when deleting a commit

[Giuseppe Scrivano <gscrivano src gnome org>]

commit 646fe139e6c64595c4c2f4fbac33ff28f2259ddf
Author: Giuseppe Scrivano <gscrivan redhat com>
Date:   Wed Oct 28 12:10:27 2015 +0100

    repo: create a tombstone commit when deleting a commit
    
    When a commit is deleted and the repo is configured to use tombstone
    commits, create one.  Delete the tombstone file only if the commit is
    pulled again.
    
    Signed-off-by: Giuseppe Scrivano <gscrivan redhat com>

 src/libostree/ostree-repo-commit.c |   22 ++++++++++++++++++++++
 src/libostree/ostree-repo.c        |   24 ++++++++++++++++++++++++
 2 files changed, 46 insertions(+), 0 deletions(-)
---
diff --git a/src/libostree/ostree-repo-commit.c b/src/libostree/ostree-repo-commit.c
index 68008c5..62da0e3 100644
--- a/src/libostree/ostree-repo-commit.c
+++ b/src/libostree/ostree-repo-commit.c
@@ -770,6 +770,28 @@ write_object (OstreeRepo         *self,
                                         cancellable, error))
         goto out;
 
+
+      if (objtype == OSTREE_OBJECT_TYPE_COMMIT)
+        {
+          GError *local_error = NULL;
+          /* If we are writing a commit, be sure there is no tombstone for it.
+             We may have deleted the commit and now we are trying to pull it again.  */
+          if (!ostree_repo_delete_object (self,
+                                          OSTREE_OBJECT_TYPE_TOMBSTONE_COMMIT,
+                                          actual_checksum,
+                                          cancellable,
+                                          &local_error))
+            {
+              if (g_error_matches (local_error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND))
+                g_clear_error (&local_error);
+              else
+                {
+                  g_propagate_error (error, local_error);
+                  goto out;
+                }
+            }
+        }
+
       if (OSTREE_OBJECT_TYPE_IS_META (objtype))
         {
           if (G_UNLIKELY (file_object_length > OSTREE_MAX_METADATA_WARN_SIZE))
diff --git a/src/libostree/ostree-repo.c b/src/libostree/ostree-repo.c
index 43dcb2b..1f1cba2 100644
--- a/src/libostree/ostree-repo.c
+++ b/src/libostree/ostree-repo.c
@@ -3202,6 +3202,30 @@ ostree_repo_delete_object (OstreeRepo           *self,
       goto out;
     }
 
+  /* If the repository is configured to use tombstone commits, create one when deleting a commit.  */
+  if (objtype == OSTREE_OBJECT_TYPE_COMMIT)
+    {
+      gboolean tombstone_commits = FALSE;
+      GKeyFile *readonly_config = ostree_repo_get_config (self);
+      if (!ot_keyfile_get_boolean_with_default (readonly_config, "core", "tombstone-commits", FALSE,
+                                                &tombstone_commits, error))
+        goto out;
+
+      if (tombstone_commits)
+        {
+          g_autoptr(GVariantBuilder) builder = NULL;
+          builder = g_variant_builder_new (G_VARIANT_TYPE ("a{sv}"));
+          g_variant_builder_add (builder, "{sv}", "commit", g_variant_new_bytestring (sha256));
+          if (!ostree_repo_write_metadata_trusted (self,
+                                                   OSTREE_OBJECT_TYPE_TOMBSTONE_COMMIT,
+                                                   sha256,
+                                                   g_variant_builder_end (builder),
+                                                   cancellable,
+                                                   error))
+            goto out;
+        }
+    }
+
   ret = TRUE;
  out:
   return ret;