fix: sync command region handling and bucket region auto-detection

[gchait]

Fix: Sync command region handling and auto-detection

Problem

This PR fixes two related issues with region handling in s5cmd:

1. Sync command doesn't respect --source-region and --destination-region flags: While the cp command correctly applies these flags, the sync command ignores them, causing operations to fail when syncing between buckets in different regions.

2. Region auto-detection fails when AWS profile has a region configured: When a profile specifies a region, the current code skips bucket region auto-detection. This causes signature mismatch errors when the actual bucket is in a different region than the profile's configured region.

Solution

1. Apply region flags in sync command (command/sync.go)

Modified getSourceAndDestinationObjects() to create separate storage option objects for source and destination clients, applying the respective region flags before creating the clients. This matches the pattern already used in the cp command.

// Create source client with source region
srcOpts := s.storageOpts
if s.srcRegion != "" {
    srcOpts.SetRegion(s.srcRegion)
}
sourceClient, err := storage.NewClient(ctx, srcurl, srcOpts)

// Create destination client with destination region
dstOpts := s.storageOpts
if s.dstRegion != "" {
    dstOpts.SetRegion(s.dstRegion)
}
destClient, err := storage.NewClient(ctx, dsturl, dstOpts)

2. Always auto-detect bucket regions (storage/s3.go)

Modified setSessionRegion() to always perform bucket region auto-detection when a bucket is specified, regardless of whether a region is configured in the profile. This makes s5cmd's behavior consistent with AWS CLI.

Changes:

• Always call GetBucketRegion() when a bucket name is provided
• Fall back to configured region only when auto-detection fails
• Only skip auto-detection when no bucket is specified (bucket-less operations)

This approach aligns with AWS CLI's "it just works" philosophy, where cross-region operations work transparently.

Notes

The extra HEAD request for bucket region auto-detection is a minor overhead (one per bucket per session) that enables seamless cross-region operations, matching user expectations from AWS CLI.

Related Issues

Fixes issues where:

• s5cmd sync --source-region us-east-1 --destination-region eu-west-1 's3://bucket1/*' s3://bucket2/ would fail
• Using AWS profiles with region configurations would cause signature mismatches for buckets in different regions

[gchait]

Regarding the failing CI, I considered adding public.ecr.aws/ to your minio image ref in the workflow (bitnami repo images are removed from Docker Hub but not from ECR).
But, there are already 2 other PRs with fixes for this.