bundle2: make header reading optional The `readbundle` function will consume the 4 first bytes to dispatch between various unbundler. We introduce a way to inform `unbundle20` that the header has been read and it can be trusted.

bundle2: prepare readbundle to return more that one type of bundle We first read 4 bytes to get the `HG10` bytes then we read the compression scheme if this is `HG10`. This prepares the code for the arrival of `HG20` handling.

bundle2: add a ui argument to readbundle The bundle2 unbundler needs a ui argument. We are now passing this information to `readbundle`.

bundle2: move `readbundle` into the `exchange` module The `readbundle` function is going to understand the bundle2 header. We move the function to a more suitable place before making any other changes.

bundle2: use headerless HG10UN stream in changegroup Using `readbundle` in the part handlers creates a circular import hell. We are now using a simple `HG10UN` stream with no header. Some parameters may later be introduced on the part to change parameter. Producers are updated as well.

bundle2: allow using bundle2 for push We now support bundle2 for local push. The unbundle function has to detect which version of the bundle to use since the return type is different. Note that push error handling is currently nonexistent. This is one of the reasons why bundle2 is still disabled by default.

bundle2: add a "check:heads" handler This part is intended to hold the same role as the `heads` argument of the unbundle function. The client fill it with the known heads at bundle time and the server will abort if its heads changed.

repoview: make the conversion from node to rev explicit while computing hidden You cannot use `repo[...]` lookup here. 1. It is slow 2. It is very likely to trigger a hidden computation itself, entering an infinite loop.

repoview: drop duplicated lookup We are already looking for local tags on the line above. We can safely drop this extra lookup.

hgweb: adding branch, tags, bookmarks, user, and file list to rss feed entries

hgweb: adding branch, tags, bookmarks, user, and file list to atom feed entries

patchbomb: warn when emailing a dirty working directory parent

tests: coverage of convert and filemap include and the default of include all

largefiles: remove no more referred "getoutgoinglfiles()"

largefiles: use "outgoinghooks" to avoid redundant outgoing check Before this patch, "hg outgoing" invokes "findcommonoutgoing()" not only in "commands.outgoing()" but also in "overrides.overrideoutgoing()" (via "getoutgoinglfiles()"), when largefiles is enabled. The latter is redundant. This patch uses "outgoinghooks" to avoid redundant outgoing check. Newly introduced function "overrides.outgoinghook()" is registered into "outgoinghooks" to get the result of outgoing check in "commands.outgoing()". It invokes "lfutil.getlfilestoupload()" directly with the result of outgoing check to avoid redundant outgoing check in "getoutgoinglfiles()": "sort()" is needed, because "lfutil.getlfilestoupload()" doesn't sort the result of it. This patch also omits "if toupload is None" ("No remote repo") case, because failure of looking remote repository up should raise exception in "commands.outgoing()" before invocation of "outgoinghooks". Newly added "hg outgoing --large --graph" tests examine "outgoinghooks" invocations in "hg outgoing --graph" code path.

outgoing: introduce "outgoinghooks" to avoid redundant outgoing check This patch introduces "outgoinghooks" to avoid redundant outgoing check for "hg outgoing" in other than "commands.outgoing" (or utility functions used by it).