tests: add more test coverage of phase changes when pushing Prepare for test coverage of phase updates with future push --readonly option, both with and without actually pushing changesets.

mergecopies: invoke _computenonoverlap for both base and tca during merges The algorithm of _checkcopies can only walk backwards in the DAG, never forward. Because of this, the two _checkcopies patches need to run from their respective endpoints to the TCA to cover the entire subgraph where the merge is being performed. However, detection of files new in both endpoints, as well as directory rename detection, need to run with respect to the merge base, so we need lists of new files both from the TCA's and the merge base's viewpoint to correctly detect renames in a graft-like merge scenario. (Series reworked by Pierre-Yves David)

copies: make it possible to distinguish betwen _computenonoverlap invocations _computenonoverlap needs to be invoked twice during a graft, and debugging messages should be distinguishable between the two invocations

copies: make _checkcopies handle simple renames in a rotated DAG This introduces a distinction between "merge base" and "topological common ancestor". During a regular merge, these two are identical. Graft, however, performs a merge in a rotated DAG, where the merge base will not be a common ancestor at all in the original DAG. To correctly find copies in case of a graft, we need to take both the merge base and the topological CA into account, and track any renames between them in reverse. Fortunately we can detect this in advance, see comment in the code about "backwards". This patch only supports finding non-divergent renames contained entirely between the merge base and the topological CA. Further patches are coming to support more complex cases. (Pierre-Yves David was involved in the cleanup of this patch.)

copies: compute a suitable TCA if base turns out to be unsuitable This will be used later in an update to _checkcopies. (Pierre-Yves David was involved in the cleanup of this patch.)

copies: detect graft-like merges Right now, nothing changes as a result of this, but we want to handle grafts differently from ordinary merges later. (Series developed together with Pierre-Yves David)

tests: introduce tests for grafting through renames These cover all currently known cases of renames being grafted, or changes being grafted through renames. Right now, most of these cases are broken. Later patches in this series will make them behave correctly. The testcases heavily rely on each other, which would make it very difficult to separate them and add them one-by-one for each case fixed by a patch. Separating them should perhaps be a 4.1 task, if it doesn't slow down the tests too much. (Developed together with Pierre-Yves David)

largefiles: fix 'deleted' files sometimes persistently appearing with R status A code snippet that has been around since largefiles was introduced was wrong: Standins no longer found in lfdirstate has *not* been removed - they have probably just been deleted ... or not created. This wrong reporting did that 'up -C' didn't undo the change and didn't sync the two dirstates. Instead of reporting such files as removed, propagate the deletion to the standin file and report the file as deleted.

largefiles: more safe handling of interruptions while updating modifications Largefiles are fragile with the design where dirstate and lfdirstate must be kept in sync. To be less fragile, mark all clean largefiles as unsure ("normallookup") before updating standins. After standins have been updated and we know exactly which largefile standins actually was changed, mark the unchanged largefiles back to clean ("normal"). This will make the failure mode more safe. If interrupted, the next command will continue to perform extra hashing of all largefiles. That will do that all largefiles that are out of sync with their standin will be marked dirty and they will show up in status and can be cleaned with update --clean.

largefiles: test coverage of fatal interruption of update Test using existing changesets in a clean working directory, revealing problems with files that don't show up as modified or do show up as removed when they just not have been written yet.