util.system: avoid buffering of subprocess output when it is piped util.system() copies subprocess' output through pipe if output file is not stdout. Because a file iterator has internal buffering, output won't be flushed until enough data is available. Therefore, it could easily miss important messages such as "waiting for lock".

bundle2: client side support for a part to import external bundles Bundle2 opens doors to advanced features allowing to reduce load on mercurial servers, and improve clone experience for users on unstable or slow networks. For instance, it could be possible to pre-generate a bundle of a repository, and give a pointer to it to clients cloning the repository, followed by another changegroup with the remainder. For significantly big repositories, this could come as several base bundles with e.g. 10k changesets, which, combined with checkpoints (not part of this change), would prevent users with flaky networks from starting over any time their connection fails. While the server-side support for those features doesn't exist yet, it is preferable to have client-side support for this early-on, allowing experiments on servers only requiring a vanilla client with bundle2 enabled.

bundle2: remove _getbundleextrapart Extensions can now add new part generators with the getbundle2partsgenerator decorator instead.

glossary: add deprecated and experimental

test-merge5: remove obsolete '-y' and its motivating comment The '-y' in 'hg update -y' was once needed to answer questions about modify/delete conflicts. That is no longer needed, so remove the '-y' and the comment justifying its use.

test-resolve.t: use redirection to /dev/null instead of grep -q