server: introduce a 'experimental.single-head-per-branch' option When the option is set, the repository will reject any transaction adding multiple heads to the same named branch. For now we reject all scenario with multiple heads. One could imagine handling closed branches differently. We prefer to keep things simple for now. The feature might get extended later. Branch closing is not the best experience Mercurial has to offer anyway.

scmutil: extra utility to display a reasonable amount of nodes Push have some logic to display a reasonable amount nodes. We extract it to an utility function to make it reusable.

uncommit: unify functions _uncommitdirstate and _unamenddirstate to one The _unamenddirstate() function was inspired by _uncommitdirstate() function as the logic was same but we were unable to use the latter function directly. So previous patch introduced the _unamenddirstate() function and now this patch unifies both the function and we have a _fixdirstate() function. Adding function in previous patch and unifying in a later patch makes the reasoning easier and also leaves the last patch dedicated to what it is meant to be. Differential Revision: https://phab.mercurial-scm.org/D971

unamend: move fb extension unamend to core unamend extension adds an unamend command which undoes the effect of the amend command. This patch moves the unamend command from that extension to uncommit extension and this one does not completely undoes the effect of amend command as it creates a new commit, rather than reviving the old one back. This also adds tests for the same. .. feature:: A new unamend command in uncommit extension which undoes the effect of the amend command by creating a new changeset which was there before amend and moving the changes that were amended to the working directory. Differential Revision: https://phab.mercurial-scm.org/D821