Remove duplicate bunidiff code from hgdiff, importing from mdiff.py instead

bash_completion: ignore hg help error messages They are usually not useful when you're completing stuff and end up cluttering the screen.

bash_completion: always use single quotes with compgen -W This avoids a bug in bash 2.05a

bash_completion: be more careful about whitespaces - use awk to parse the output of hg help. - print one completion candidate per line - print the debug commands after regular commands (this eases the shell side of the parsing) - don't print aliases that are simple abbreviations (e.g. up/update, id/identify)