add stemcellmetadata package

refactor: move stemcell metadata loading to a separate package
refactor: improve error message in stemcellmetadata.SlugParts

main/compile.go

@@ -10,6 +10,7 @@ import (
 	"github.com/cloudfoundry/bosh-agent/app"
 	"github.com/cloudfoundry/bosh-agent/releasetarball"
 	"github.com/cloudfoundry/bosh-agent/settings/directories"
+	"github.com/cloudfoundry/bosh-agent/stemcellmetadata"
 )
 
 func compileTarball(command string, args []string) {
@@ -22,7 +23,7 @@ func compileTarball(command string, args []string) {
 		log.Fatal(err)
 	}
 
-	stemcellOS, stemcellName, stemcellVersion, err := readStemcellSlug()
+	stemcellOS, stemcellName, stemcellVersion, err := stemcellmetadata.SlugParts()
 	if err != nil {
 		log.Fatal(err)
 	}

stemcellmetadata/slug.go

@@ -0,0 +1,10 @@
+//go:build !linux
+
+package stemcellmetadata
+
+import "log"
+
+func SlugParts() (_ string, _ string, _ string, _ error) {
+	log.Fatal("func readStemcellSlug (in package stemcellmetadata) is not implemented for GOOS != linux")
+	return
+}

main/stemcell_linux.go → stemcellmetadata/slug_linux.go

@@ -1,4 +1,4 @@
-package main
+package stemcellmetadata
 
 import (
 	"bufio"
@@ -10,7 +10,7 @@ import (
 	"strings"
 )
 
-func readStemcellSlug() (string, string, string, error) {
+func SlugParts() (string, string, string, error) {
 	stemcellVersionBuf, err := os.ReadFile("/var/vcap/bosh/etc/stemcell_version")
 	if err != nil {
 		return "", "", "", err