hgweb_mod.archive(): Use 'key' instead of builtin 'id'.

Remove useless variable assignments in util.opener. The original idea might have been to prevent circular references, but as this assignment would have created another reference, this makes no difference.

identify: work with remote repos

identify: add support for output flags

identify: accept a revision argument

identify: use contexts

context: add tags() method

identify: show nullid for empty repo

Backed out changeset cfa477946181824f4c769580ebf59710090ba08a Only printenv was changed, not the actual execution of hooks. And not setting an empty value might cause problems on platforms which can't always remove variables from the environment.

Adjust note about variables not being set for empty values.