feat(ssh): support BREV_SSH_CONFIG_FILE env var override

Allow users to specify a custom SSH config file path via the
BREV_SSH_CONFIG_FILE environment variable. When set, brev commands
(refresh, etc.) will edit the specified file instead of ~/.ssh/config.

This is useful for nix-managed systems where the main SSH config
is read-only.

Author: ishandhanani

pkg/files/files.go

@@ -74,6 +74,9 @@ func GetSSHPrivateKeyPath(home string) string {
 }
 
 func GetUserSSHConfigPath(home string) (string, error) {
+	if override := os.Getenv("BREV_SSH_CONFIG_FILE"); override != "" {
+		return override, nil
+	}
 	sshConfigPath := filepath.Join(home, ".ssh", "config")
 	return sshConfigPath, nil
 }