[PATCH 0 of 4 V3] isolation between each local repositories handled in a same process at a time

[FUJIWARA Katsunori]

This patch series fixes some problem about isolation between each
local repositories handled in a same process at a time.

The message shown at error detection was refined, from V2 to V3.

For issue2904, patches posted by Simon Heimberg at Oct 4 seems to
fix it completely: in this patch, I only focus on command
execution locally.

    http://selenic.com/pipermail/mercurial-devel/2012-October/044858.html

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