fix: more robust docker context problem handling

See coop-cloud/organising#325
See coop-cloud/organising#340

pkg/context/context.go

@@ -2,6 +2,7 @@ package context
 
 import (
 	"errors"
+	"fmt"
 
 	"github.com/docker/cli/cli/command"
 	dConfig "github.com/docker/cli/cli/config"
@@ -42,3 +43,34 @@ func GetContextEndpoint(ctx contextStore.Metadata) (string, error) {
 func newContextStore(dir string, config contextStore.Config) contextStore.Store {
 	return contextStore.New(dir, config)
 }
+
+// MissingContextMsg helps end-uers debug missing docker context issues.
+var missingContextMsg = `unable to find Docker context for %s?
+
+Please run "abra server ls" to confirm. If you see "unknown" in the table
+output then you need to run the following command:
+
+    abra server add %s <args>
+
+See "abra server add --help" for more.
+`
+
+// HasDockerContext figures out if a local setup has a working docker context
+// configuration or not. This usually tells us if they'll be able to make a SSH
+// connection to a server or not and can be a useful way to signal to end-users
+// that they need to fix something up if missing.
+func HasDockerContext(serverName string) error {
+	dockerContextStore := NewDefaultDockerContextStore()
+	contexts, err := dockerContextStore.Store.List()
+	if err != nil {
+		return err
+	}
+
+	for _, ctx := range contexts {
+		if ctx.Name == serverName {
+			return nil
+		}
+	}
+
+	return fmt.Errorf(missingContextMsg, serverName, serverName)
+}