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.

checkcopies: add a sanity check against false-positive copies When grafting a copy backwards through a rename, a copy is wrongly detected, which causes the graft to be applied inappropriately, in a destructive way. Make sure that the old file name really exists in the common ancestor, and bail out if it doesn't. This fixes the aggravated case of bug 5343, although the basic issue (failure to duplicate the copy information) still occurs.

exchange: refactor APIs to obtain bundle data (API) Currently, exchange.getbundle() returns either a cg1unpacker or a util.chunkbuffer (in the case of bundle2). This is kinda OK, as both expose a .read() to consumers. However, localpeer.getbundle() has code inferring what the response type is based on arguments and converts the util.chunkbuffer returned in the bundle2 case to a bundle2.unbundle20 instance. This is a sign that the API for exchange.getbundle() is not ideal because it doesn't consistently return an "unbundler" instance. In addition, unbundlers mask the fact that there is an underlying generator of changegroup data. In both cg1 and bundle2, this generator is being fed into a util.chunkbuffer so it can be re-exposed as a file object. util.chunkbuffer is a nice abstraction. However, it should only be used "at the edges." This is because keeping data as a generator is more efficient than converting it to a chunkbuffer, especially if we convert that chunkbuffer back to a generator (as is the case in some code paths currently). This patch refactors exchange.getbundle() into exchange.getbundlechunks(). The new API returns an iterator of chunks instead of a file-like object. Callers of exchange.getbundle() have been updated to use the new API. There is a minor change of behavior in test-getbundle.t. This is because `hg debuggetbundle` isn't defining bundlecaps. As a result, a cg1 data stream and unpacker is being produced. This is getting fed into a new bundle20 instance via bundle2.writebundle(), which uses a backchannel mechanism between changegroup generation to add the "nbchanges" part parameter. I never liked this backchannel mechanism and I plan to remove it someday. `hg bundle` still produces the "nbchanges" part parameter, so there should be no user-visible change of behavior. I consider this "regression" a bug in `hg debuggetbundle`. And that bug is captured by an existing "TODO" in the code to use bundle2 capabilities.