Add an `export` builtin, and API to write to libarchive

At the moment I'm looking at using rpm-ostree to manage RPM inputs
which can then be converted into Docker images.  It's most convenient
if we can stream directly out of libostree rather than doing a
checkout + tar combination.

There are also backup/debugging etc. reasons to implement `export` as
well.

1 files changed, 148 insertions, 0 deletions

diff --git a/src/ostree/ot-builtin-export.c b/src/ostree/ot-builtin-export.c
new file mode 100644
index 00000000..2d350b8c
--- /dev/null
+++ b/src/ostree/ot-builtin-export.c
@@ -0,0 +1,148 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2016 Colin Walters <walters@verbum.org>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "ot-main.h"
+#include "ot-builtins.h"
+#include "ostree.h"
+#include "ostree-repo-file.h"
+#include "otutil.h"
+
+#ifdef HAVE_LIBARCHIVE
+#include <archive.h>
+#include <archive_entry.h>
+#endif
+
+static char *opt_output_path;
+static gboolean opt_no_xattrs;
+
+static GOptionEntry options[] = {
+  { "no-xattrs", 0, 0, G_OPTION_ARG_NONE, &opt_no_xattrs, "Skip output of extended attributes", NULL },
+  { "output", 'o', 0, G_OPTION_ARG_STRING, &opt_output_path, "Output to PATH ", "PATH" },
+  { NULL }
+};
+
+#ifdef HAVE_LIBARCHIVE
+
+static void
+propagate_libarchive_error (GError      **error,
+                            struct archive *a)
+{
+  g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+               "%s", archive_error_string (a));
+}
+
+#endif
+
+gboolean
+ostree_builtin_export (int argc, char **argv, GCancellable *cancellable, GError **error)
+{
+  GOptionContext *context;
+  glnx_unref_object OstreeRepo *repo = NULL;
+  gboolean ret = FALSE;
+  const char *rev;
+  g_autoptr(GFile) root = NULL;
+  g_autofree char *commit = NULL;
+  g_autoptr(GVariant) commit_data = NULL;
+  struct archive *a;
+  OstreeRepoArchiveOptions opts = { 0, };
+
+  context = g_option_context_new ("COMMIT - Stream COMMIT to stdout in tar format");
+
+  if (!ostree_option_context_parse (context, options, &argc, &argv, OSTREE_BUILTIN_FLAG_NONE, &repo, cancellable, error))
+    goto out;
+
+#ifdef HAVE_LIBARCHIVE  
+
+  if (argc <= 1)
+    {
+      ot_util_usage_error (context, "A COMMIT argument is required", error);
+      goto out;
+    }
+  rev = argv[1];
+
+  a = archive_write_new ();
+  /* Yes, this is hardcoded for now.  There is
+   * archive_write_set_format_filter_by_ext() but it's fairly magic.
+   * Many programs have support now for GNU tar, so should be a good
+   * default.  I also don't want to lock us into everything libarchive
+   * supports.
+   */
+  if (archive_write_set_format_gnutar (a) != ARCHIVE_OK)
+    {
+      propagate_libarchive_error (error, a);
+      goto out;
+    }
+  if (archive_write_add_filter_none (a) != ARCHIVE_OK)
+    {
+      propagate_libarchive_error (error, a);
+      goto out;
+    }
+  if (opt_output_path)
+    {
+      if (archive_write_open_filename (a, opt_output_path) != ARCHIVE_OK)
+        {
+          propagate_libarchive_error (error, a);
+          goto out;
+        }
+    }
+  else
+    {
+      if (archive_write_open_FILE (a, stdout) != ARCHIVE_OK)
+        {
+          propagate_libarchive_error (error, a);
+          goto out;
+        }
+    }
+
+  if (opt_no_xattrs)
+    opts.disable_xattrs = TRUE;
+
+  if (!ostree_repo_read_commit (repo, rev, &root, &commit, cancellable, error))
+    goto out;
+
+  if (!ostree_repo_load_variant (repo, OSTREE_OBJECT_TYPE_COMMIT, commit, &commit_data, error))
+    goto out;
+
+  opts.timestamp_secs = ostree_commit_get_timestamp (commit_data);
+
+  if (!ostree_repo_write_tree_to_archive (repo, &opts, (OstreeRepoFile*)root, a,
+                                          cancellable, error))
+    goto out;
+
+  if (archive_write_close (a) != ARCHIVE_OK)
+    {
+      propagate_libarchive_error (error, a);
+      goto out;
+    }
+
+#else
+  g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_SUPPORTED,
+               "This version of ostree is not compiled with libarchive support");
+  goto out;
+#endif  
+  
+  ret = TRUE;
+ out:
+  if (context)
+    g_option_context_free (context);
+  return ret;
+}