JavaHL RFE: ISVNRemote should provide API to retrieve a contents of a specific file

[Marc Strapetz]

To allow users to browse through all contents of a file (as part of an 
interactive blame), it's necessary to have an efficient API to retrieve 
these file contents.

AFAIU, the low-level file_rev_handler already provides this information 
via svn_txdelta_window_handler_t. Unfortunately, in RemoteSettion.cpp 
this information is converted to just a boolean (delta_handler != NULL) 
and passed to the JavaHL callback afterwards.

I don't think it's necessary (or even desirable) to provide the 
patch/stream logic, like svn_stream_open_readonly, as Java API, just a 
way to retrieve complete file contents for all revisions. Suggestion:

interface ISVNRemote {
/**
 *  @param RemoteFileContentsCallback may be null
 */
void getFileRevisions(String path,
                      long startRevision, long endRevision,
                      boolean includeMergedRevisions,
                      RemoteFileRevisionsCallback handler
                      RemoteFileContentsCallback contentsHandler)
  throws ClientException;
}

interface RemoteFileContentsCallback {
    void doFileContent(ISVNRemote.FileRevision fileRevision,
                       InputStream content);
}

-Marc