Add support for ostree static-delta delete

Closes: #245
Approved by: giuseppe

src/libostree/ostree-cmdprivate.c

@@ -46,7 +46,8 @@ ostree_cmd__private__ (void)
 {
   static OstreeCmdPrivateVTable table = {
     impl_ostree_generate_grub2_config,
-    _ostree_repo_static_delta_dump
+    _ostree_repo_static_delta_dump,
+    _ostree_repo_static_delta_delete
   };
 
   return &table;

src/libostree/ostree-cmdprivate.h

@@ -27,6 +27,7 @@ G_BEGIN_DECLS
 typedef struct {
   gboolean (* ostree_generate_grub2_config) (OstreeSysroot *sysroot, int bootversion, int target_fd, GCancellable *cancellable, GError **error);
   gboolean (* ostree_static_delta_dump) (OstreeRepo *repo, const char *delta_id, GCancellable *cancellable, GError **error);
+  gboolean (* ostree_static_delta_delete) (OstreeRepo *repo, const char *delta_id, GCancellable *cancellable, GError **error);
 } OstreeCmdPrivateVTable;
 
 /* Note this not really "public", we just export the symbol, but not the header */

src/libostree/ostree-repo-static-delta-core.c

@@ -782,6 +782,41 @@ _ostree_delta_needs_byteswap (GVariant *superblock)
     }
 }
 
+gboolean
+_ostree_repo_static_delta_delete (OstreeRepo                    *self,
+                                  const char                    *delta_id,
+                                  GCancellable                  *cancellable,
+                                  GError                      **error)
+{
+  gboolean ret = FALSE;
+  g_autofree char *from = NULL;
+  g_autofree char *to = NULL;
+  g_autofree char *deltadir = NULL;
+  struct stat buf;
+
+  _ostree_parse_delta_name (delta_id, &from, &to);
+  deltadir = _ostree_get_relative_static_delta_path (from, to, NULL);
+
+  if (fstatat (self->repo_dir_fd, deltadir, &buf, 0) != 0)
+    {
+      if (errno == ENOENT)
+        g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND,
+                     "Can't find delta %s", delta_id);
+      else
+        glnx_set_error_from_errno (error);
+
+      goto out;
+    }
+
+  if (!glnx_shutil_rm_rf_at (self->repo_dir_fd, deltadir,
+                             cancellable, error))
+    goto out;
+
+  ret = TRUE;
+ out:
+  return ret;
+}
+
 gboolean
 _ostree_repo_static_delta_dump (OstreeRepo                    *self,
                                 const char                    *delta_id,

src/libostree/ostree-repo-static-delta-private.h

@@ -196,6 +196,12 @@ _ostree_repo_static_delta_dump (OstreeRepo                 *repo,
                                 GCancellable               *cancellable,
                                 GError                    **error);
 
+gboolean
+_ostree_repo_static_delta_delete (OstreeRepo                 *repo,
+                                  const char                 *delta_id,
+                                  GCancellable               *cancellable,
+                                  GError                    **error);
+
 /* Used for static deltas which due to a historical mistake are
  * inconsistent endian.
  *