push: restrict common discovery to the pushed set This changeset make use of the ability of the set discovery to only search common changeset for a subset of the repository. Restricting that search to the pushed set avoid potential waste of time finding out the status of many unrelated related revision. Repository with many heads were especially badly affected by this. Here is an example of findcommonhead discovery for pushing 11 outgoing changeset on a repository with tens of thousand of unrelated heads. (discovery run over a ssh link to localhost). Before: queries: 92 time: 44.1996s After: queries: 3 time: 0.6938s A x63 speedup even with a network link without latency.

setdiscover: allow to ignore part of the local graph Currently, the push discovery first determines the full set of common nodes before looking into what changesets are outgoing. When pushing a specific subset, this can lead to pathological situations where we search for the status of thousand of local heads that are unrelated to the requested pushes. To fix this, we need to teach the discovery to ignores part of the graph. Most of the necessary pieces were already in place. This changeset just makes them available to higher level API and tests them. Change actually impacting pushes are coming in a later changeset.

largefiles: allow to run 'debugupgraderepo' on repo with largefiles The extensions wrap the necessary function to ensure the 'largefiles' requirements won't be dropped. It is now possible to run `hg debugupgraderepo` on a repository with largefiles.

upgraderepo: allow extension to register preserved requirements Some requirement does not directly result from config and needs more advanced logic to be preserved. The current example is 'largefiles'. We add a hook point in the upgrade code so that extensions can handle these cases. The 'largefiles' extension will use it in the next changeset.

revset: make follow() accept empty startrev This is the same behavior as ancestors(emptyset).

revset: alias follow(startrev=rev) to ancestors(rev) This seems natural given 'log -frREV' (with no file pattern) is equivalent to 'log -frREV *'.

revset: make follow() accept keyword arguments Also renamed the argument from 'pattern' to 'file' conforming to followlines().

revset: make follow() accept multiple startrevs The diff might look slightly complicated, but the initial "c = repo['.']" was effective if rev = None.

dagop: use heap to compute max rev in filectxancestors()

dagop: add smartset interface to filectxancestors() The original filectx API is kept public since we'll need it to walk ancestor (rev, match) pairs efficiently. The current implementation scans ancestors twice for 'hg log -fp FILE'.

overlayworkingctx: add `_checkexist(path)` This is in preparation to switch this class to inheriting (and being based off a) `commitctx` instead of a `workingctx`. `filectx` has no `exists` function, so this is how we'll fall back in that case. Differential Revision: https://phab.mercurial-scm.org/D1237

overlayworkingctx: fix a bad reference to `self._path` Differential Revision: https://phab.mercurial-scm.org/D1236

overlayworkingctx: track copy information in the context We can no longer do so in the dirstate, so add the functions to do so here. Differential Revision: https://phab.mercurial-scm.org/D1235

rebaseruntime: raise InMemoryMergeConflictsError on merge conflicts Differential Revision: https://phab.mercurial-scm.org/D1234

rebase: do not bail on uncomitted changes if rebasing in-memory Differential Revision: https://phab.mercurial-scm.org/D1233