Tart: auto-detect the guest OS to use a proper Cirrus CI Agent binary (#724)

Author: edigaryev

internal/executor/instance/persistentworker/isolation/tart/tart.go

@@ -266,8 +266,20 @@ func (tart *Tart) Run(ctx context.Context, config *runconfig.RunConfig) (err err
 
 	tart.logger.Debugf("IP %s retrieved from VM %s, running agent...", ip, tart.vm.Ident())
 
+	// Try to determine the agent OS, falling back to "darwin"
+	// in case anything goes wrong to preserve the old behavior
+	agentOS := "darwin"
+
+	info, err := tart.vm.Info(ctx)
+	if err != nil {
+		tart.logger.Debugf("failed to auto-detect the VM's operating system, assuming %q", agentOS)
+	} else if info.OS != "" {
+		agentOS = info.OS
+		tart.logger.Debugf("successfully auto-detected the VM's operating system as %q", agentOS)
+	}
+
 	err = remoteagent.WaitForAgent(ctx, tart.logger, fmt.Sprintf("%s:%d", ip, tart.sshPort),
-		tart.sshUser, tart.sshPassword, "darwin", "arm64",
+		tart.sshUser, tart.sshPassword, agentOS, "arm64",
 		config, true, initializeHooks, terminateHooks, "",
 		map[string]string{"CIRRUS_VM_ID": tart.vm.Ident()})
 	if err != nil {

internal/executor/instance/persistentworker/isolation/tart/vm.go

@@ -2,6 +2,7 @@ package tart
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"github.com/cirruslabs/echelon"
 	"github.com/getsentry/sentry-go"
@@ -21,6 +22,10 @@ type VM struct {
 	errChan            chan error
 }
 
+type Info struct {
+	OS string `json:"os"`
+}
+
 type directoryMount struct {
 	Name     string
 	Path     string
@@ -197,6 +202,21 @@ func (vm *VM) RetrieveIP(ctx context.Context) (string, error) {
 	return strings.TrimSpace(stdout), nil
 }
 
+func (vm *VM) Info(ctx context.Context) (*Info, error) {
+	stdout, _, err := Cmd(ctx, vm.env, "get", "--format", "json", vm.ident)
+	if err != nil {
+		return nil, err
+	}
+
+	var info Info
+
+	if err := json.Unmarshal([]byte(stdout), &info); err != nil {
+		return nil, err
+	}
+
+	return &info, nil
+}
+
 func (vm *VM) Close() error {
 	ctx := context.Background()