S3: Support a region= configuration useful for some non-Amazon S3
implementations. This feature needs git-annex to be built with aws-0.24.
datacenter= sets both the AWS hostname and region in one setting, which is
easy when using AWS, but not useful for other hosts. So kept datacenter
as-is, but added this additional config.
Sponsored-By: Brett Eisenberg on Patreon
This does mean it has to run ldd once per executable, which is actually
quite a number of times, so will be a bit slower.
Sponsored-by: Luke Shumaker on Patreon
See commit e04a931439 for an explanation
of why move uses transfer stages for --from, but command stages for
--to. At the point of that commit, copy was actually already using
command stages for everything, so the commit was incorrect about
improving copy --to.
But, the same reasoning about --from applies to copy as to move; when
verification is not done incrementally, download and verification are
the main two stages. The cleanup stage for copy is even less work than
for move (it doesn't drop from the remote).
Sponsored-by: Dartmouth College's DANDI project
Use separate stages for download and upload. In the common case where
it downloads the file from one remote and then uploads to the other,
those are by far the most expensive operations, and there's a decent
chance the two remotes bottleneck on different resources.
Suppose it's being run with -J2 and a bunch of 10 mb files. Two threads
will be started both downloading from the src remote. They will probably
finish at the same time. Then two threads will be started uploading to
the dst remote. They will probably take the same time as well. Before
this change, it would alternate back and forth, bottlenecking on src and dst.
With this change, as soon as the two threads start uploading to dst, two
more threads are able to start, downloading from src. So bandwidth to
both remotes is saturated more often.
Other commands that use transferStages only send in one direction at a
time. So the worker threads for the other direction will sit idle, and
there will be no change in their behavior.
Sponsored-by: Dartmouth College's DANDI project
