Spent ages tracking down a memory leak in the assistant that showed up when
a lot of files were added. Turned out to be a standard haskell laziness
induced problem, fixed by adding strictness annotations. Actually there
were several of them, that leaked at different rates. Eventually, I seem to
have gotten them all fixed:

Before: [[bugs/import_memleak_from_the_assistant/leakbefore.png]]
After: [[bugs/import_memleak_from_the_assistant/leakafter.png]]

Also fixed a bug in `git annex add` when the disk was completely full.
In that situation, it could sometimes move the file from the work tree to
.git/annex/objects and fail to put the symlink in place.
