check-code: added a check for calls to the builtin cmp function

manifest: removed usage of the global cmp function Py3k doesn't have a global cmp() function, making this call problematic in the py3k port. Also, calling cmp() here is not necessary, since we only want to know if the two values are equal. A check for equality perfect in this case and this patch does that.

tests: run check-code.py on working directory files If we insist on Mercurial sources to pass check-code.py, let automate the process and make it part of the tests. Objections?

minor style fix: hgext/rebase.py:157 -- line too long found by a run of check-code

zsh completions: add qpush --move option

Merge with stable

chunkbuffer: use += rather than cStringIO to reduce memory footprint This significantly refactors the read() loop to use a queue of chunks. The queue is alternately filled to at least 256k and then emptied by concatenating onto the output buffer. For very large read sizes, += uses less memory because it can resize the target string in place.

httprepo: decompress stream incrementally to reduce memory usage

verify: initialize rp variable in case we hit out of memory

merge: drop reference to file contents after write This reduces memory usage on large consecutive gets.

revlog: drop cache after use to save memory footprint If we reconstruct back to back large versions, we need to drop the cache first to avoid doubling memory usage.

verify: reduce memory footprint when unpacking files By never holding a reference to the unpacked string, we avoid holding two consecutive large files in memory.

verify: report exceptions that don't have a str() method

color: fix test-diff-color breakage