Add cross region transfer support

[igungor]

Currently s5cmd doesn't support cp/mv operations between different s3 buckets. We need a way to specify the source region via a flag.

awscli provides --source-region <value> flag to support this feature.

[TomGudman]

I believe I have the same problem. I am trying to move a bucket to a different region. Unfortunately, it seems s5cmd expects the source and destination buckets to be in the same region.

Example of copying from the us-west-2 to eu-west-1 (in the purpose of moving)

AWS_DEFAULT_REGION=us-west-2  s5cmd cp s3://source-us/* s3://destination-eu/
[..]
ERROR "cp s3://source-us/file1 s3://destination-us/file1": BucketRegionError: incorrect region, the bucket is not in 'us-west-2' region at endpoint '' status code: 301, request id: , host id:
[..]

I would suggest something similar to @igungor but what's best : --source-region or --destination-region?

In the mean time, I will revert to s4cmd, then s3cmd and finally awscli if it turns out to be that complicated to copy cross region ;-)

[igungor]

Though it doesn't matter that much whether if it's source-region or destination-region, I think the former is better since we have familiarity from awscli.