exchange: expose bundle2 capabilities on pulloperation This adds a cache and makes accessing the capabilities slightly simpler, as you don't need to directly go through the bundle2 module. This will also help prevent a function-level import in streamclone.py. This patch arguably isn't necessary. But I think it makes things slightly nicer.

keyword: make restrict mode False while updating files for rollback This is a preparation for using 'repo.rollback()' instead of aborting a current running transaction for "shelve" and "unshelve". Before this patch, updating files as a part of 'repo.rollback()' overridden by keyword extension always follows 'restrict' mode of the command currently executed. "merge", "unshelve" and so on should be 'restrict'-ed, because keyword expansion may cause unexpected conflicts at merging while these commands. But, if 'repo.rollback()' is invoked while executing 'restrict'-ed commands, modified files in the working directory are marked as "CLEAN" unexpectedly by code path below: # 'lookup' below is True at updating modified files for rollback kwcmd = self.restrict and lookup # kwexpand/kwshrink : if kwcmd: self.repo.dirstate.normal(f) On the other hand, "rollback" command isn't 'restrict'-ed, because rollbacking itself doesn't imply merging. Therefore, disabling 'restrict' mode while updating files as a part of 'repo.rollback()' regardless of current 'restrict' mode should be reasonable.

streamclone: rename and document maybeperformstreamclone() Upcoming patches will introduce bundle2 based streaming clones. Add "legacy" to the function name and add a docstring clarifying the intent of the function.

streamclone: move applyremotedata() into maybeperformstreamclone() Future work around stream cloning will be implemented in a bundle2 world. This code will only be used in the legacy code path and doesn't need to be abstracted or extensible.

branchmap: move branch cache code out of streamclone.py This is low-level branch map and cache manipulation code. It deserves to live next to similar code in branchmap.py. Moving it also paves the road for multiple consumers, such as a bundle2 part handler that receives branch mappings from a remote. This is largely a mechanical move, with only variable names and indentation being changed.

streamclone: move streamin() into maybeperformstreamclone() streamin() only had a single consumer. And it always only ever will because it is strongly coupled with the current, soon-to-be-superseded-by-bundle2 functionality. The return value has been dropped because nobody was using it.

streamclone: refactor maybeperformstreamclone to take a pullop Just like all the other pull steps. Consistency is good. This seems a little excessive right now since maybeperformstreamclone is such a short function. This will be addressed in a subsequent patch.

demandimport: replace more references to _demandmod instances _demandmod instances may be referenced by multiple importing modules. Before this patch, the _demandmod instance only maintained a reference to its first consumer when using the "from X import Y" syntax. This is because we only created a single _demandmod instance (attached to the parent X module). If multiple modules A and B performed "from X import Y", we'd produce a single _demandmod instance "demandmod" with the following references: X.Y = <demandmod> A.Y = <demandmod> B.Y = <demandmod> The locals from the first consumer (A) would be stored in <demandmod1>. When <demandmod1> was loaded, we'd look at the locals for the first consumer and replace the symbol, if necessary. This resulted in state: X.Y = <module> A.Y = <module> B.Y = <demandmod> B's reference to Y wasn't updated and was still using the proxy object because we just didn't record that B had a reference to <demandmod> that needed updating! With this patch, we add support for tracking which modules in addition to the initial importer have a reference to the _demandmod instance and we replace those references at module load time. In the case of posix.py, this fixes an issue where the "encoding" module was being proxied, resulting in hundreds of thousands of __getattribute__ lookups on the _demandmod instance during dirstate operations on mozilla-central, speeding up execution by many milliseconds. There are likely several other operation that benefit from this change as well. The new mechanism isn't perfect: references in locals (not globals) may likely linger. So, if there is an import inside a function and a symbol from that module is used in a hot loop, we could have unwanted overhead from proxying through _demandmod. Non-global imports are discouraged anyway. So hopefully this isn't a big deal in practice. We could potentially deploy a code checker that bans use of attribute lookups of function-level-imported modules inside loops. This deficiency in theory could be avoided by storing the set of globals and locals dicts to update in the _demandmod instance. However, I tried this and it didn't work. One reason is that some globals are _demandmod instances. We could work around this, but it's a bit more work. There also might be other module import foo at play. The solution as implemented is better than what we had and IMO is good enough for the time being. It's worth noting that this sub-optimal behavior was made worse by the introduction of absolute_import and its recommended "from . import X" syntax for importing modules from the "mercurial" package. If we ever wrote performance tests, measuring the amount of module imports and __getattribute__ proxy calls through _demandmod instances would be something I'd have it check.