util: enable "hooks" to return list of the values returned from each hooks

summary: separate checking incoming/outgoing and showing remote summary This patch separates checking incoming/outgoing and showing remote summary, as a preparation for refactoring in succeeding patches, because: - checking incoming/outgoing may be needed, even if "--remote" is not specified for "hg summary" - checking incoming/outgoing may not be needed simultaneously "hg summary --large" without "--remote" is typical case for these.

largefiles: reuse "findcommonoutgoing()" result at "hg push" Before this patch, "hg push" invokes "findcommonoutgoing()" not only in "exchange.push()" but also in "lfilesrepo.push()", when largefiles is enabled. The latter is redundant. This patch registers own "prepushoutgoinghook" function into "prepushoutgoinghooks" of "localrepository" to reuse "findcommonoutgoing()" result. "prepushoutgoinghook" omits "changelog.nodesbetween()" invocation, because "findcommonoutgoing()" invocation in "exchange.push()" takes "onlyheads" argument and it considers "nodesbetween()".

localrepo: introduce "prepushoutgoinghooks" to extend outgoing check easily This patch introduces "prepushoutgoinghooks" to extend outgoing check before pushing changesets to remote easily. This chooses the function returning "util.hooks" instead of the one to be overridden. The latter may cause problems silently, if one of overriders forgets (or fails) to execute a kind of "super(xxx, self).overridden(...)". In the other hand, the former can ensure that all registered functions are invoked, unless one of them raises an exception.