[ostree] repo: Never delete .commitmeta files

[Matthew Barnes <mbarnes src gnome org>]

commit df75fc232a3d9191be6e2393400a2eff9602f43a
Author: Matthew Barnes <mbarnes redhat com>
Date:   Mon Nov 23 11:04:31 2015 -0500

    repo: Never delete .commitmeta files
    
    Do not delete a .commitmeta file after removing the last metadata entry.
    This way a client will pull the empty .commitmeta file and overwrite old
    metadata as expected.
    
    https://bugzilla.gnome.org/750459

 src/libostree/ostree-repo-commit.c    |   32 +++++++++++++++-----------------
 src/ostree/ot-builtin-trivial-httpd.c |    3 ++-
 tests/test-commit-sign.sh             |    9 +++++++++
 3 files changed, 26 insertions(+), 18 deletions(-)
---
diff --git a/src/libostree/ostree-repo-commit.c b/src/libostree/ostree-repo-commit.c
index 732bbd0..bee58ca 100644
--- a/src/libostree/ostree-repo-commit.c
+++ b/src/libostree/ostree-repo-commit.c
@@ -2140,30 +2140,28 @@ ostree_repo_write_commit_detached_metadata (OstreeRepo      *self,
       normalized_size = g_variant_get_size (normalized);
     }
 
-  if (normalized_size == 0)
+  if (normalized_size > 0)
     {
-      GError *local_error = NULL;
-
-      (void) g_file_delete (metadata_path, cancellable, &local_error);
-
-      if (g_error_matches (local_error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND))
-        {
-          g_clear_error (&local_error);
-        }
-      else if (local_error != NULL)
+      if (!g_file_replace_contents (metadata_path,
+                                    g_variant_get_data (normalized),
+                                    g_variant_get_size (normalized),
+                                    NULL, FALSE, 0, NULL,
+                                    cancellable, error))
         {
-          g_propagate_error (error, local_error);
-          g_prefix_error (error, "Unable to delete detached metadata: ");
+          g_prefix_error (error, "Unable to write detached metadata: ");
           goto out;
         }
     }
   else
     {
-      if (!g_file_replace_contents (metadata_path,
-                                    g_variant_get_data (normalized),
-                                    g_variant_get_size (normalized),
-                                    NULL, FALSE, 0, NULL,
-                                    cancellable, error))
+      g_autoptr(GFileOutputStream) output_stream = NULL;
+
+      /* Don't write to the stream, leave the file empty. */
+      output_stream = g_file_replace (metadata_path,
+                                      NULL, FALSE,
+                                      G_FILE_CREATE_NONE,
+                                      cancellable, error);
+      if (output_stream == NULL)
         {
           g_prefix_error (error, "Unable to write detached metadata: ");
           goto out;
diff --git a/src/ostree/ot-builtin-trivial-httpd.c b/src/ostree/ot-builtin-trivial-httpd.c
index d770189..c6a3757 100644
--- a/src/ostree/ot-builtin-trivial-httpd.c
+++ b/src/ostree/ot-builtin-trivial-httpd.c
@@ -273,7 +273,8 @@ do_get (OtTrivialHttpd    *self,
           buffer = soup_buffer_new_with_owner (g_mapped_file_get_contents (mapping),
                                                buffer_length,
                                                mapping, (GDestroyNotify)g_mapped_file_unref);
-          soup_message_body_append_buffer (msg->response_body, buffer);
+          if (buffer->length > 0)
+            soup_message_body_append_buffer (msg->response_body, buffer);
           soup_buffer_free (buffer);
         }
       else /* msg->method == SOUP_METHOD_HEAD */
diff --git a/tests/test-commit-sign.sh b/tests/test-commit-sign.sh
index 2288d09..0dfbb76 100755
--- a/tests/test-commit-sign.sh
+++ b/tests/test-commit-sign.sh
@@ -119,4 +119,13 @@ ${CMD_PREFIX} ostree --repo=${test_tmpdir}/ostree-srv/gnomerepo gpg-sign --gpg-h
 ${CMD_PREFIX} ostree --repo=repo pull origin main
 ${CMD_PREFIX} ostree --repo=repo show main | grep -o 'Found [[:digit:]] signature' > show
 assert_file_has_content show 'Found 1 signature'
+
+# Delete the signature from the commit so the detached metadata is empty,
+# then pull and verify the signature is also deleted on the client side.
+${CMD_PREFIX} ostree --repo=${test_tmpdir}/ostree-srv/gnomerepo gpg-sign --gpg-homedir=${SRCDIR}/gpghome 
--delete main $keyid
+${CMD_PREFIX} ostree --repo=repo pull origin main
+if ${CMD_PREFIX} ostree --repo=repo show main | grep -o 'Found [[:digit:]] signature'; then
+  assert_not_reached
+fi
+
 rm -rf repo gnomerepo-files