changegroup: add bundlecaps back Commit 282b288aa20c333c removed the unused bundlecaps argument from the changegroup code. While it is unused in core Mercurial, it was an important feature for the remotefilelog extension because it allowed the exchange layer to communicate to the changegroup packer that this was a shallow repo and that filelogs should not be included. Without bundlecaps, there is currently no other way to pass that information along without a more extensive refactor of exchange, bundle, and changegroup code. This patch backs out the original removal, and merges it with some recent changes to changegroup apis.

flagprocessor: add a fast path when flags is 0 When flags is 0, _processflags could be a no-op instead of iterating through the flag bits.

shelve: make shelvestate use simplekeyvaluefile Currently shelvestate uses line ordering to differentiate fields. This makes it hard for extensions to wrap shelve, since if two alternative versions of code add a new line, correct merging is going to be problematic. simplekeyvaluefile was introduced fot this purpose specifically. After this patch: - shelve will always write a simplekeyvaluefile - unshelve will check the first line of the file for a version, and if the version is 1, will read it in a position-based way, if the version is 2, will read it in a key-value way As discussed with Yuya previously, this will be able to handle old-style shelvedstate files, but old Mercurial versions will fail on the attempt to read shelvedstate file of version 2 with a self-explanatory message: 'abort: this version of shelve is incompatible with the version used in this repo'