revlog: break up compression of large deltas Python's zlib apparently makes an internal copy of strings passed to compress(). To avoid this, compress strings 1M at a time, then join them at the end if the result would be smaller than the original. For initial commits of large but compressible files, this cuts peak memory usage nearly in half.

revlog: fix caching of buffer objects

chunkiter: handle large reads more efficiently - for large reads, don't attempt to read more than necessary - if we've gathered the exact number of bytes needed, avoid a string copy