Write out hgrc properly. Previously, we simply appended to the hgrc file, which meant that it ended up containing multiple "paths" sections. Now, we only modify "paths.default".

patchbomb: continue if we can't import readline.

Get test-commit to exit cleanly.

Commit date validation: more stringent checks, more useful error messages.

revlog: raise informative exception if file is missing.

Minor cleanups.

Created a class in util called chunkbuffer that buffers reads from an iterator over strings (aka chunks). Also added to util (for future use) is a generator function that iterates over a file n bytes at a time. Lastly, localrepo was changed to use this new chunkbuffer class when reading changegroups form the local repository.

Add test output.

Date validation must check for 32-bit width. Don't use assert to check.

Make date/timezone validation in changelog.add more robust. Add test.