lib/repo: Add an API to mark a commit as partial

For the [rpm-ostree jigdo ♲📦](https://github.com/projectatomic/rpm-ostree/issues/1081) work.
We're basically doing "pull" via a non-libostree mechanism, and this
should be fully supported.  As I mentioned earlier we should try to
have `ostree-repo-pull.c` only use public APIs; this gets us closer
to that.

Closes: #1376
Approved by: jlebon

apidoc/ostree-sections.txt

@@ -320,6 +320,7 @@ ostree_repo_set_alias_ref_immediate
 ostree_repo_set_cache_dir
 ostree_repo_sign_delta
 ostree_repo_has_object
+ostree_repo_mark_commit_partial
 ostree_repo_write_metadata
 ostree_repo_write_metadata_async
 ostree_repo_write_metadata_finish

src/libostree/libostree-devel.sym

@@ -21,6 +21,7 @@
 
 LIBOSTREE_2017.15 {
   ostree_repo_fsck_object;
+  ostree_repo_mark_commit_partial;
 } LIBOSTREE_2017.14;
 
 /* Stub section for the stable release *after* this development one; don't

src/libostree/ostree-repo-commit.c

@@ -1589,6 +1589,48 @@ ensure_txn_refs (OstreeRepo *self)
                                                        g_free);
 }
 
+/**
+ * ostree_repo_mark_commit_partial:
+ * @self: Repo
+ * @checksum: Commit SHA-256
+ * @is_partial: Whether or not this commit is partial
+ * @error: Error
+ *
+ * Commits in "partial" state do not have all their child objects written. This
+ * occurs in various situations, such as during a pull, but also if a "subpath"
+ * pull is used, as well as "commit only" pulls.
+ *
+ * This function is used by ostree_repo_pull_with_options(); you
+ * should use this if you are implementing a different type of transport.
+ *
+ * Since: 2017.15
+ */
+gboolean
+ostree_repo_mark_commit_partial (OstreeRepo     *self,
+                                 const char     *checksum,
+                                 gboolean        is_partial,
+                                 GError        **error)
+{
+  g_autofree char *commitpartial_path = _ostree_get_commitpartial_path (checksum);
+  if (is_partial)
+    {
+      glnx_autofd int fd = openat (self->repo_dir_fd, commitpartial_path,
+                                   O_EXCL | O_CREAT | O_WRONLY | O_CLOEXEC | O_NOCTTY, 0644);
+      if (fd == -1)
+        {
+          if (errno != EEXIST)
+            return glnx_throw_errno_prefix (error, "open(%s)", commitpartial_path);
+        }
+    }
+  else
+    {
+      if (!ot_ensure_unlinked_at (self->repo_dir_fd, commitpartial_path, 0))
+        return FALSE;
+    }
+
+  return TRUE;
+}
+
 /**
  * ostree_repo_transaction_set_refspec:
  * @self: An #OstreeRepo

src/libostree/ostree-repo-prune.c

@@ -36,16 +36,6 @@ typedef struct {
   guint64 freed_bytes;
 } OtPruneData;
 
-static gboolean
-prune_commitpartial_file (OstreeRepo    *repo,
-                          const char    *checksum,
-                          GCancellable  *cancellable,
-                          GError       **error)
-{
-  g_autofree char *path = _ostree_get_commitpartial_path (checksum);
-  return ot_ensure_unlinked_at (repo->repo_dir_fd, path, error);
-}
-
 static gboolean
 maybe_prune_loose_object (OtPruneData        *data,
                           OstreeRepoPruneFlags    flags,
@@ -68,7 +58,7 @@ maybe_prune_loose_object (OtPruneData        *data,
 
           if (objtype == OSTREE_OBJECT_TYPE_COMMIT)
             {
-              if (!prune_commitpartial_file (data->repo, checksum, cancellable, error))
+              if (!ostree_repo_mark_commit_partial (data->repo, checksum, FALSE, error))
                 return FALSE;
             }
 

src/libostree/ostree-repo-pull.c

@@ -558,21 +558,6 @@ fetch_uri_contents_utf8_sync (OstreeFetcher  *fetcher,
                                                 cancellable, error);
 }
 
-static gboolean
-write_commitpartial_for (OtPullData *pull_data,
-                         const char *checksum,
-                         GError **error)
-{
-  g_autofree char *commitpartial_path = _ostree_get_commitpartial_path (checksum);
-  glnx_autofd int fd = openat (pull_data->repo->repo_dir_fd, commitpartial_path, O_EXCL | O_CREAT | O_WRONLY | O_CLOEXEC | O_NOCTTY, 0644);
-  if (fd == -1)
-    {
-      if (errno != EEXIST)
-        return glnx_throw_errno_prefix (error, "open(%s)", commitpartial_path);
-    }
-  return TRUE;
-}
-
 static void
 enqueue_one_object_request (OtPullData                *pull_data,
                             const char                *checksum,
@@ -1267,7 +1252,7 @@ meta_fetch_on_complete (GObject           *object,
                                             pull_data->cancellable, error))
             goto out;
 
-          if (!write_commitpartial_for (pull_data, checksum, error))
+          if (!ostree_repo_mark_commit_partial (pull_data->repo, checksum, TRUE, error))
             goto out;
         }
 
@@ -1821,7 +1806,7 @@ scan_one_metadata_object (OtPullData                 *pull_data,
       if (objtype == OSTREE_OBJECT_TYPE_COMMIT)
         {
           /* mark as partial to ensure we scan the commit below */
-          if (!write_commitpartial_for (pull_data, checksum, error))
+          if (!ostree_repo_mark_commit_partial (pull_data->repo, checksum, TRUE, error))
             return FALSE;
         }
 
@@ -1854,7 +1839,7 @@ scan_one_metadata_object (OtPullData                 *pull_data,
           if (objtype == OSTREE_OBJECT_TYPE_COMMIT)
             {
               /* mark as partial to ensure we scan the commit below */
-              if (!write_commitpartial_for (pull_data, checksum, error))
+              if (!ostree_repo_mark_commit_partial (pull_data->repo, checksum, TRUE, error))
                 return FALSE;
             }
           if (!_ostree_repo_import_object (pull_data->repo, refd_repo,
@@ -4340,15 +4325,13 @@ ostree_repo_pull_with_options (OstreeRepo             *self,
     {
       GLNX_HASH_TABLE_FOREACH_V (requested_refs_to_fetch, const char*, checksum)
         {
-          g_autofree char *commitpartial_path = _ostree_get_commitpartial_path (checksum);
+          if (!ostree_repo_mark_commit_partial (pull_data->repo, checksum, FALSE, error))
-          if (!ot_ensure_unlinked_at (pull_data->repo->repo_dir_fd, commitpartial_path, 0))
             goto out;
         }
 
       GLNX_HASH_TABLE_FOREACH_V (commits_to_fetch, const char*, commit)
         {
-          g_autofree char *commitpartial_path = _ostree_get_commitpartial_path (commit);
+          if (!ostree_repo_mark_commit_partial (pull_data->repo, commit, FALSE, error))
-          if (!ot_ensure_unlinked_at (pull_data->repo->repo_dir_fd, commitpartial_path, 0))
             goto out;
         }
     }

src/libostree/ostree-repo.h

@@ -362,6 +362,12 @@ gboolean      ostree_repo_abort_transaction (OstreeRepo     *self,
                                              GCancellable   *cancellable,
                                              GError        **error);
 
+_OSTREE_PUBLIC
+gboolean      ostree_repo_mark_commit_partial (OstreeRepo     *self,
+                                               const char     *checksum,
+                                               gboolean        is_partial,
+                                               GError        **error);
+
 _OSTREE_PUBLIC
 void          ostree_repo_transaction_set_refspec (OstreeRepo *self,
                                                    const char *refspec,