BigString (reducing peak memory)

[Martin Pool]

> Why is the whole file needed in memory at once?
> If it is read into a string, it would be quite easy to create a "virtual"
> string handling "paging" of the file.

If it's easy, please send us a patch :)

The problem is not so much reading the file in multiple chunks rather
than as a single string, but rather making sure that it is never
combined back in to one chunk as it is processed in being moved
between repository, working tree, network, etc.

-- 
Martin