hgwebdir: show nested repositories (issue1336)

patch/diff: use a separate function to write the first line of a file diff

patch: consolidate two different regexes for parsing of git diffs

patch: extract local function addmodehdr

help: show extension commands in short list, separate extension list in help In 'hg', we now show a short list of commands, including extension commands. In 'hg help', we show core commands, a list of enabled extensions, and topics.

help: show help topics by default in 'hg help', with longest available id

mail: correct typo in variable name

merge with crew

mail: test patch mime encoding for patchbomb

patchbomb: mime-encode clean utf-8 patches (issue814) Fixes issue814, but only for utf.

mail: mime-encode patches that are utf-8 utf-8 can be safely detected without making assumptions on the encoding/locale used by the recipient. Content-Transfer-Encoding for utf-8 patches is base64 (default of python's email module).

Some additional space/tab cleanups

merge with crew-stable, again

merge with crew-stable