code: @Post("/projects/{projectName}/repos/{repoName}/preview")
      public CompletableFuture<Iterable<ChangeDto<?>>> preview(
              @Param("revision") @Default("-1") String revision,
              Repository repository,
              @RequestConverter(ChangesRequestConverter.class) Iterable<Change<?>> changes) {
  
          final CompletableFuture<Map<String, Change<?>>> changesFuture =
                  repository.previewDiff(new Revision(revision), changes);
  
          return changesFuture.thenApply(previewDiffs -> previewDiffs.values().stream()
                                                                     .map(DtoConverter::convert)
                                                                     .collect(toImmutableList()));
      }
docs: POST /projects/{projectName}/repos/{repoName}/preview?revision={revision}
  
  <p>Previews the actual changes which will be resulted by the given changes.