Brev 8959/fix unix socket len macos

[abhtripathi]

Problem

ControlPath for SSH ControlMaster is a Unix domain socket. The previous format ~/.ssh/brev-control-%r@%h-%p built the path from remote user, host, and port. On long hostnames (e.g. some AWS EC2 names such as ec2-3-90-240-200.compute-1.amazonaws.com), the path could exceed 104 characters—macOS’s limit for Unix socket paths—leading to:

unix_listener: path "..." too long for Unix domain socket

brev shell did not surface this well: it failed with only an SSH exit code and no clear message.

Changes

ControlPath (ssh.go, sshconfigurer.go, sshconfigurer_test.go)

• Before: ControlPath ~/.ssh/brev-control-%r@%h-%p
• After: ControlPath ~/.ssh/brev-control-%C

%C is SSH’s 40‑character SHA1 of the connection parameters, so the path no longer depends on hostname length. It remains unique per connection, same as %r@%h-%p, with no other behavior change.

Error handling (pkg/cmd/shell/shell.go)

• SSH stderr is handled with io.MultiWriter so output still appears on the terminal in real time, while failures can be explained.
• If the error matches a ControlPath / socket path length problem, the message tells users to run brev refresh so their SSH config is regenerated.
• For other SSH failures, a short generic hint also points to brev refresh.

Users who have not run brev refresh and still have the old ControlPath in their SSH config will see a clear explanation instead of a silent or opaque failure.