Move xattr handling into libgsystem, fix sysroot to handle directory ownership/perms

This large patch moves the core xattr logic down into libgsystem,
which allows the gs_shutil_cp_a() API to copy them.  In turn, this
allows us to just use that API instead of rolling our own recursive
copy here.

As noted in the new comment though, one case that we are explicitly
regressing is where the new /etc removes a parent directory that's
needed by a modified file.  This seems unlikely for most vendors now,
but let's do that as a separate bug.

https://bugzilla.gnome.org/show_bug.cgi?id=711058

src/libostree/ostree-sysroot-deploy.c

@@ -23,27 +23,33 @@
 #include "config.h"
 
 #include "ostree-sysroot-private.h"
+#include "ostree-core-private.h"
 #include "otutil.h"
 #include "libgsystem.h"
 
 /**
- * copy_one_config_file:
+ * copy_modified_config_file:
  *
  * Copy @file from @modified_etc to @new_etc, overwriting any existing
- * file there.
+ * file there.  The @file may refer to a regular file, a symbolic
+ * link, or a directory.  Directories will be copied recursively.
+ *
+ * Note this function does not (yet) handle the case where a directory
+ * needed by a modified file is deleted in a newer tree.
  */
 static gboolean
-copy_one_config_file (GFile              *orig_etc,
-                      GFile              *modified_etc,
-                      GFile              *new_etc,
-                      GFile              *src,
-                      GCancellable       *cancellable,
-                      GError            **error)
+copy_modified_config_file (GFile              *orig_etc,
+                           GFile              *modified_etc,
+                           GFile              *new_etc,
+                           GFile              *src,
+                           GCancellable       *cancellable,
+                           GError            **error)
 {
   gboolean ret = FALSE;
   gs_unref_object GFileInfo *src_info = NULL;
+  gs_unref_object GFileInfo *parent_info = NULL;
   gs_unref_object GFile *dest = NULL;
-  gs_unref_object GFile *parent = NULL;
+  gs_unref_object GFile *dest_parent = NULL;
   gs_free char *relative_path = NULL;
   
   relative_path = g_file_get_relative_path (modified_etc, src);
@@ -55,49 +61,28 @@ copy_one_config_file (GFile              *orig_etc,
   if (!src_info)
     goto out;
 
+  dest_parent = g_file_get_parent (dest);
+  if (!ot_gfile_query_info_allow_noent (dest_parent, OSTREE_GIO_FAST_QUERYINFO, G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
+                                        &parent_info, cancellable, error))
+    goto out;
+  if (!parent_info)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_NOT_FOUND,
+                   "New tree removes parent directory '%s', cannot merge",
+                   gs_file_get_path_cached (dest_parent));
+      goto out;
+    }
+
+  if (!gs_shutil_rm_rf (dest, cancellable, error))
+    goto out;
+
   if (g_file_info_get_file_type (src_info) == G_FILE_TYPE_DIRECTORY)
     {
-      gs_unref_object GFileEnumerator *src_enum = NULL;
-      gs_unref_object GFileInfo *child_info = NULL;
-      GError *temp_error = NULL;
-
-      /* FIXME actually we need to copy permissions and xattrs */
-      if (!gs_file_ensure_directory (dest, TRUE, cancellable, error))
+      if (!gs_shutil_cp_a (src, dest, cancellable, error))
         goto out;
-
-      src_enum = g_file_enumerate_children (src, OSTREE_GIO_FAST_QUERYINFO,
-                                            G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
-                                            cancellable, error);
-
-      while ((child_info = g_file_enumerator_next_file (src_enum, cancellable, error)) != NULL)
-        {
-          gs_unref_object GFile *child = g_file_get_child (src, g_file_info_get_name (child_info));
-
-          if (!copy_one_config_file (orig_etc, modified_etc, new_etc, child,
-                                     cancellable, error))
-            goto out;
-        }
-      g_clear_object (&child_info);
-      if (temp_error != NULL)
-        {
-          g_propagate_error (error, temp_error);
-          goto out;
-        }
     }
   else
     {
-      parent = g_file_get_parent (dest);
-
-      /* FIXME actually we need to copy permissions and xattrs */
-      if (!gs_file_ensure_directory (parent, TRUE, cancellable, error))
-        goto out;
-      
-      /* We unlink here because otherwise gio throws an error on
-       * dangling symlinks.
-       */
-      if (!ot_gfile_ensure_unlinked (dest, cancellable, error))
-        goto out;
-
       if (!g_file_copy (src, dest, G_FILE_COPY_OVERWRITE | G_FILE_COPY_NOFOLLOW_SYMLINKS | G_FILE_COPY_ALL_METADATA,
                         cancellable, NULL, NULL, error))
         goto out;
@@ -169,16 +154,16 @@ merge_etc_changes (GFile          *orig_etc,
     {
       OstreeDiffItem *diff = modified->pdata[i];
 
-      if (!copy_one_config_file (orig_etc, modified_etc, new_etc, diff->target,
-                                 cancellable, error))
+      if (!copy_modified_config_file (orig_etc, modified_etc, new_etc, diff->target,
+                                      cancellable, error))
         goto out;
     }
   for (i = 0; i < added->len; i++)
     {
       GFile *file = added->pdata[i];
 
-      if (!copy_one_config_file (orig_etc, modified_etc, new_etc, file,
-                                 cancellable, error))
+      if (!copy_modified_config_file (orig_etc, modified_etc, new_etc, file,
+                                      cancellable, error))
         goto out;
     }