ostree export: Accept treeish in place of commit

If there is a commit the timestamp is set to the commit time - otherwise
it's set to 1970-01.01T00:00Z.

In the future `ostree export` could be taught to handle blobs as well.

src/ostree/ot-builtin-export.c

@@ -27,6 +27,7 @@
 #include "ostree-libarchive-private.h"
 #include "ostree.h"
 #include "ostree-repo-file.h"
+#include "ostree-cmdprivate.h"
 
 #ifdef HAVE_LIBARCHIVE
 #include <archive.h>
@@ -69,7 +70,7 @@ ostree_builtin_export (int argc, char **argv, OstreeCommandInvocation *invocatio
   g_autoptr(GOptionContext) context = NULL;
   g_autoptr(OstreeRepo) repo = NULL;
   gboolean ret = FALSE;
-  g_autoptr(GFile) root = NULL;
+  g_autoptr(OstreeRepoFile) root = NULL;
   g_autoptr(GFile) subtree = NULL;
   g_autofree char *commit = NULL;
   g_autoptr(GVariant) commit_data = NULL;
@@ -130,22 +131,23 @@ ostree_builtin_export (int argc, char **argv, OstreeCommandInvocation *invocatio
   if (opt_no_xattrs)
     opts.disable_xattrs = TRUE;
 
-  if (!ostree_repo_read_commit (repo, rev, &root, &commit, cancellable, error))
+  if (!ostree_cmd__private__ ()->ostree_repo_open_file (
+          repo, rev, opt_subpath, OSTREE_REPO_OPEN_FILE_EXPECT_TREE, &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 (commit)
+    {
+      if (!ostree_repo_load_variant (repo, OSTREE_OBJECT_TYPE_COMMIT, commit,
+                                     &commit_data, error))
+        goto out;
 
-  if (opt_subpath)
-    subtree = g_file_resolve_relative_path (root, opt_subpath);
-  else
-    subtree = g_object_ref (root);
+      opts.timestamp_secs = ostree_commit_get_timestamp (commit_data);
+    }
 
   opts.path_prefix = opt_prefix;
 
-  if (!ostree_repo_export_tree_to_archive (repo, &opts, (OstreeRepoFile*)subtree, a,
+  if (!ostree_repo_export_tree_to_archive (repo, &opts, root, a,
                                            cancellable, error))
     goto out;
 

tests/test-export.sh

@@ -25,7 +25,7 @@ set -euo pipefail
 
 setup_test_repository "archive"
 
-echo '1..5'
+echo '1..6'
 
 $OSTREE checkout test2 test2-co
 $OSTREE commit --no-xattrs -b test2-noxattrs -s "test2 without xattrs" --tree=dir=test2-co
@@ -49,6 +49,15 @@ assert_file_empty diff.txt
 
 echo 'ok export --subpath gnutar diff (no xattrs)'
 
+cd ${test_tmpdir}
+${OSTREE} 'export' :test2-noxattrs:baz -o test2-subpath.tar
+mkdir t2a
+(cd t2a && tar xf ../test2-subpath.tar)
+${CMD_PREFIX} ostree --repo=repo diff --no-xattrs ./t2a ./t/baz > diff.txt
+assert_file_empty diff.txt
+
+echo 'ok export treeish gnutar diff (no xattrs)'
+
 cd ${test_tmpdir}
 ${OSTREE} 'export' test2-noxattrs --prefix=the-prefix/ -o test2-prefix.tar
 mkdir t3