This ensures file propigate takes place in situations such as: Usb drive A
is connected to B. A's master branch is already in sync with B, but it is
being used to sneakernet some files around, so B downloads those. There is no
master branch change, so C does not request these files. B needs to upload
the files it just downloaded on to C, etc.
My first try at this, I saw loops happen. B uploaded to C, which then
tried to upload back to B (because it had not received the updated
git-annex branch from B yet). B already had the file, but it still created
a transfer info file from the incoming transfer, and its watcher saw
that be removed, and tried to upload back to C.
These loops should have been fixed by my previous commit. (They never
affected ssh remotes, only local ones, it seemed.) While C might still try
to upload to B, or to some other remote that already has the file, the
extra work dies out there.
This seems to work pretty well.
Handled the process groups like this:
- git-annex processes started by the assistant for transfers are run in their
own process groups.
- otherwise, rely on the shell to allocate a process group for git-annex
There is potentially a problem if some other program runs git-annex
directly (not using sh -c) The program and git-annex would then be in
the same process group. If that git-annex starts a transfer and it's
canceled, the program would also get killed. May or may not be a desired
result.
Also, the new updateTransferInfo probably closes a race where it was
possible for the thread id to not be recorded in the transfer info, if
the transfer info file from the transfer process is read first.
I've convinced myself that nothing in DaemonStatus can deadlock,
as it always keepts the TMVar full. That was the only reason it was in the
Annex monad.
This should fix OSX/BSD issues with not noticing transfer information
files with kqueue. Now that threads are used, the thread can manage the
transfer slot allocation and deallocation by itself; much cleaner.
There's still a bug; if the child updates its transfer info file,
then the data from it will superscede the TransferInfo, losing the
info that we should wait on this child.
