[PATCH 0 of 2 STABLE V2] annotation: fix problems in the filelog merging the revision and its ancestor

[FUJIWARA Katsunori]

This patch series fixes issue3841.

Points shown below are different from previous post:

  - add test to examine whether issue3841 is fixed or not

    this series describes also points causing issue3841 in filelog of
    "mercurial/commands.py" in the repository of Mercurial itself as
    example.

  - describe more detail about condition to reproduce the issue

    the filelog which includes merging the revision and its ancestor
    can reproduce issue3841. changelog/manifest including such merging
    can't.

You'll notice one more issue in "filectx.annotation" that annotation
result for the recent common ancestor of merged revisions is kept in
"hist", even if it isn't referred any more.

I'm planning to post it separately as improvement of memory
efficiency, because it doesn't affect result of annotation.