revset: detect integer list on parsing Right now, using "%ld" with `repo.revs("…%ld…", somerevs)` is very inefficient, all items in `somerevs` will be serialized to ascii and then reparsed as integers. If `somerevs` contains just an handful of entry this is fine, however, when you get to thousands or hundreds of thousands of revisions this becomes very slow. To avoid this serialization we need to first detect this situation. The code involved in the whole process is quite complex so we start simple and focus on some "simple" but widespread cases. So far we only detect the situation and don't do anything special about it. The singled out will be serialized in `formatspec` in the same way as before.

revert: extract "%ld" formatting in a _formatintlist function We'll have to reuse this logic in different places.

revset: extract parsing logic out of formatspec We want to be able to perform better handling of some input when running revset (eg: `repo.revs("%ld", somerevs)`). The first step is to be able to access some of the parsed content before it gets substituted. There are many possible different substitutions, we'll add support for them gradually. In this changeset we support none, we just split some logic in a sub function as a preparatory step.