patch: remove unused fsbackend._join() The function lost its last caller in 2a095d3442e0 (patch: replace functions in fsbackend to use vfs, 2014-06-05) when the callers started relying on the opener to do the join.

patch: add close() to abstractbackend patchbackend() seems to call it on an arbitrary backend, so it seems to be part of the API. Since all subclasses do something in their close() methods, I decided to let this one raise an exception rather than just pass.

log: add an extension hook-point in changeset_printer Extensions sometimes wants to add other information in the default log output format (when no templating is used). Add an empty function named '_exthook' for easing the extension life. Extensions will be able to wrap this function and collaborate to display additional information. Exthook is called after displaying troubles and just before displaying the files, extra and description. Add a new test file to test it and not pollute other test files.

drawdag: support obsmarker creation in comments This patch adds special comment handling so one can create obsmarkers in drawdag comments like "# replace: A -> B -> C", "# prune: X, Y, Z", "split: P -> M, N" and they are just self-explained.

test-drawdag: add a test for drawdag.py The drawdag script is useful but does not have a formal test. This patch adds it.

filemerge: convert a couple of wvfs calls in internal mergetools to contexts One hitch is that sometimes fcd is actually an absentfilectx which does not expose any mutator functions. In order to still use the context functions, we look up the underlying workingfilectx to perform the write there. One alternate way would be to put the write functions on the absentfilectx and have them pass-through. While this makes the callsites cleaner, we would need to decide what its getter functions would return after this point, since returning None for `data` (and True for `isabsent()`) might no longer be correct after a write. I discussed with Sidd about just having the getters raise RuntimeErrors after a mutator has been called, but we actually call isabsent() in merge.py after running the internal merge tools.

configitems: support callable as a default value Yuya pointed out that using mutable value as the default could be problematic. To work around this we now support callable object as default value. This allows for creating new mutable objects on demand when needed.

obsutil: move 'getmarkers' to the new modules We have a new 'obsutil' module now. We move the high level utility there to bring 'obsolete.py' back to a more reasonable size.

obsutil: move the 'marker' class to the new modules We have a new 'obsutil' module now. We move high level utility there to bring 'obsolete.py' back to a more reasonable size.

obsolete: delete three unused utility functions None of this function has been used in the past 5 years, so I think it is safe to just kill them. All code accessing rich markers is using 'getmarkers(...)' instead (or raw markers).

obsutil: move 'foreground' to the new modules We have a new 'obsutil' module now. We move the high level utility there to bring 'obsolete.py' back to a more reasonable size.

obsutil: move 'allsuccessors' to the new modules We have a new 'obsutil' module now. We move the high level utility there to bring 'obsolete.py' back to a more reasonable size.

obsutil: move 'allprecursors' to the new modules We have a new 'obsutil' module now. We move the high level utility there to bring 'obsolete.py' back to a more reasonable size.

obsutil: move 'exclusivemarkers' to the new modules We have a new 'obsutil' module now. We move the high level utility there to bring 'obsolete.py' back to a more reasonable size.

obsutil: move 'successorssets' to the new modules We have a new 'obsutil' module now. We move this high level utility there to bring 'obsolete.py' back to a more reasonable size.

revlog: add an experimental option to mitigated delta issues (issue5480) The general delta heuristic to select a delta do not scale with the number of branch. The delta base is frequently too far away to be able to reuse a chain according to the "distance" criteria. This leads to insertion of larger delta (or even full text) that themselves push the bases for the next delta further away leading to more large deltas and full texts. This full text and frequent recomputation throw Mercurial performance in disarray. For example of a slightly large repository 280 000 files (2 150 000 versions) 430 000 changesets (10 000 topological heads) Number below compares repository with and without the distance criteria: manifest size: with: 21.4 GB without: 0.3 GB store size: with: 28.7 GB without 7.4 GB bundle last 15 00 revisions: with: 800 seconds 971 MB without: 50 seconds 73 MB unbundle time (of the last 15K revisions): with: 1150 seconds (~19 minutes) without: 35 seconds Similar issues has been observed in other repositories. Adding a new option or "feature" on stable is uncommon. However, given that this issues is making Mercurial practically unusable, I'm exceptionally targeting this patch for stable. What is actually needed is a full rework of the delta building and reading logic. However, that will be a longer process and churn not suitable for stable. In the meantime, we introduces a quick and dirty mitigation of this in the 'experimental' config space. The new option introduces a way to set the maximum amount of memory usable to store a diff in memory. This extend the ability for Mercurial to create chains without removing all safe guard regarding memory access. The option should be phased out when core has a more proper solution available. Setting the limit to '0' remove all limits, setting it to '-1' use the default limit (textsize x 4).