help: use full name of extensions to look up them for keyword search Before this patch, "hg help -k KEYWORD" fails, if there is the extension of which name includes ".", because "extensions.load()" invoked from "help.topicmatch()" fails to look such extension up, even though it is already loaded in. "help.topicmatch()" invokes "extensions.load()" with the name gotten from "extensions.enabled()". The former expects full name of extension (= key in '[extensions]' section), but the latter returns names shortened by "split('.')[-1]". This difference causes failure of looking extension up. This patch adds "shortname" argument to "extensions.enabled()" to make it return shortened names only if it is True. "help.topicmatch()" turns it off to get full name of extensions. Then, this patch shortens full name of extensions by "split('.')[-1]" for showing them in the list of extensions. Shortening is also applied on names gotten from "extensions.disabled()" but harmless, because it returns only extensions directly under "hgext" and their names should not include ".".