Index: subversion/libsvn_repos/load.c
===================================================================
--- subversion/libsvn_repos/load.c	(revision 936046)
+++ subversion/libsvn_repos/load.c	(working copy)
@@ -277,20 +277,98 @@
 {
   apr_pool_t *subpool = svn_pool_create(pool);
   apr_hash_t *mergeinfo;
+  svn_mergeinfo_t outside_mergeinfo;
   apr_hash_t *final_mergeinfo = apr_hash_make(subpool);
   apr_hash_index_t *hi;
 
   SVN_ERR(svn_mergeinfo_parse(&mergeinfo, initial_val->data, subpool));
 
-  /* Issue #3020: If the dump stream represents only part of a repository,
-     then mergeinfo in the stream may refer to revisions outside of the
-     stream.  Remove any such invalid ranges before renumbering. */
-  SVN_ERR(svn_mergeinfo__filter_mergeinfo_by_ranges(
-    &mergeinfo, mergeinfo,
-    rb->pb->youngest_old_rev, rb->pb->oldest_old_rev - 1,
-    TRUE, /* Allow only references to revs that exist in the load stream. */
-    subpool, subpool));
+  if (apr_hash_count(rb->pb->rev_map) > 0)
+    {
+      /* Find any mergeinfo which predates the start of the dump load stream. */
+      SVN_ERR(svn_mergeinfo__filter_mergeinfo_by_ranges(
+        &outside_mergeinfo, mergeinfo,
+        rb->pb->youngest_old_rev, rb->pb->oldest_old_rev - 1,
+        FALSE, /* Allow only references to revs that exist in the load stream. */
+        subpool, subpool));
+      /* Issue #3020: If the dump stream represents only part of a repository,
+         then mergeinfo in the stream may refer to revisions outside of the
+         stream.  Remove any such invalid ranges before renumbering. */
+      SVN_ERR(svn_mergeinfo__filter_mergeinfo_by_ranges(
+        &mergeinfo, mergeinfo,
+        rb->pb->youngest_old_rev, rb->pb->oldest_old_rev - 1,
+        TRUE, /* Allow only references to revs that exist in the load stream. */
+        subpool, subpool));
+    }
+  else /* No mapping, so this is the first rev loaded. */
+    {
+      outside_mergeinfo = mergeinfo;
+      mergeinfo = apr_hash_make(subpool);
+    }
 
+  /* Check the mergeinfo that predates the load stream.  If it refers
+     to path-revs that exist in the target repository keep it,
+     otherwise drop it. */
+  if (apr_hash_count(outside_mergeinfo))
+    {
+      svn_mergeinfo_t all_keeper_mergeinfo = apr_hash_make(subpool);
+
+      for (hi = apr_hash_first(subpool, outside_mergeinfo);
+           hi;
+           hi = apr_hash_next(hi))
+        {
+          const char *merge_source = svn__apr_hash_index_key(hi);
+          apr_array_header_t *rangelist = svn__apr_hash_index_val(hi);
+          svn_node_kind_t merge_source_kind;
+          struct parse_baton *pb = rb->pb;
+          int i;
+          svn_fs_root_t *root_p;
+          svn_merge_range_t *range;
+
+          for (i = 0; i < rangelist->nelts; i++)
+            {
+              int y;
+
+              range = APR_ARRAY_IDX(rangelist, i, svn_merge_range_t *);
+
+              for (y = range->start + 1; y <= range->end; y++)
+                {
+                  svn_error_t *err = svn_fs_revision_root(&root_p, pb->fs, 
+                                                          y, subpool);
+                  if (err)
+                    {
+                      if (err->apr_err == SVN_ERR_FS_NO_SUCH_REVISION)
+                        {
+                          svn_error_clear(err);
+                          continue;
+                        }
+                      return err;
+                    }
+
+                  SVN_ERR(svn_fs_check_path(&merge_source_kind, 
+                                            rb->txn_root,
+                                            merge_source, subpool));
+                  if (merge_source_kind != svn_node_none)
+                    {
+                      apr_array_header_t *keeper_rangelist =
+                        svn_rangelist__initialize(range->start, range->end,
+                                                  range->inheritable,
+                                                  subpool);
+                      svn_mergeinfo_t keeper_mergeinfo =
+                        apr_hash_make(subpool);
+                      apr_hash_set(keeper_mergeinfo, merge_source,
+                                   APR_HASH_KEY_STRING, keeper_rangelist);
+                      SVN_ERR(svn_mergeinfo_merge(all_keeper_mergeinfo,
+                                                  keeper_mergeinfo,
+                                                  subpool));
+                    }
+                }
+            }
+        }
+      if (apr_hash_count(all_keeper_mergeinfo))
+        SVN_ERR(svn_mergeinfo_merge(mergeinfo, all_keeper_mergeinfo, subpool));
+    }
+
   for (hi = apr_hash_first(subpool, mergeinfo); hi; hi = apr_hash_next(hi))
     {
       const char *merge_source;
@@ -1250,32 +1328,22 @@
 
   if (strcmp(name, SVN_PROP_MERGEINFO) == 0)
     {
-      /* If we haven't yet committed any revisions then *any* mergeinfo
-         will refer to the wrong revisions or revisions that don't exist.
-         Either way none of this mergeinfo can be valid, so remove it all. */
-      if (apr_hash_count(rb->pb->rev_map) == 0)
+      /* Renumber mergeinfo as appropriate. */
+      svn_string_t *renumbered_mergeinfo;
+
+      SVN_ERR(renumber_mergeinfo_revs(&renumbered_mergeinfo, value, rb,
+                                      nb->pool));
+      value = renumbered_mergeinfo;
+      if (parent_dir)
         {
-          value = NULL;
+          /* Prefix the merge source paths with PARENT_DIR. */
+          /* ASSUMPTION: All source paths are included in the dump
+             stream. */
+          svn_string_t *mergeinfo_val;
+          SVN_ERR(prefix_mergeinfo_paths(&mergeinfo_val, value,
+                                         parent_dir, nb->pool));
+          value = mergeinfo_val;
         }
-      else
-        {
-          /* Renumber mergeinfo as appropriate. */
-          svn_string_t *renumbered_mergeinfo;
-
-          SVN_ERR(renumber_mergeinfo_revs(&renumbered_mergeinfo, value, rb,
-                                          nb->pool));
-          value = renumbered_mergeinfo;
-          if (parent_dir)
-            {
-              /* Prefix the merge source paths with PARENT_DIR. */
-              /* ASSUMPTION: All source paths are included in the dump
-                 stream. */
-              svn_string_t *mergeinfo_val;
-              SVN_ERR(prefix_mergeinfo_paths(&mergeinfo_val, value,
-                                             parent_dir, nb->pool));
-              value = mergeinfo_val;
-            }
-        }
     }
 
   return svn_fs_change_node_prop(rb->txn_root, nb->path,