I considered inlining tx.select_diff(), but that looked a bit cryptic because
the arguments orders are reasonably different. This thin wrapper will help
enforce the common interactive editing behavior.
This moves the config loading closer to CLI args where --tool=<name> option
will be processed. The factory function are proxied through the command helper
so that the base_ignores can be attached there later.
When we abandon a working-copy commit, we create a new working-copy
commit on top. This behave is very useful, but it's not obvious. Let's
document it.
Thankfully, 2bbefcc338 (rewrite: default to not simplifying ancestor
merges) means that there are much fewer commands where we need to
document this behavior.
I'm going to add a prefix resolution method to OpStore, but OpStore is
unrelated to the index. I think ObjectId, HexPrefix, and PrefixResolution can
be extracted to this module.
It seems better to have the caller pass the transaction description
when we finish the transaction than when we start it. That way we have
all the information we want to include more readily available.
