mantle/sdk: Clean out version.go

I'm trying to make `mantle/sdk` be a coreos-assembler build metadata + mantle
integration point, since that's a lot of the role that it played
with Container Linux.

Clean out `version.go` in prep for that; only one API call is
still used, and we can clean that up in the callers after.

mantle/sdk/version.go

@@ -15,18 +15,7 @@
 package sdk
 
 import (
-	"bufio"
 	"fmt"
-	"io/ioutil"
-	"os"
-	"os/exec"
-	"path/filepath"
-	"strings"
-	"time"
-)
-
-const (
-	coreosId = "{E96281A6-D1AF-4BDE-9A0A-97B76E56DC57}"
 )
 
 type Versions struct {
@@ -36,135 +25,7 @@ type Versions struct {
 	SDKVersion string
 }
 
-func unquote(s string) string {
-	if len(s) < 2 {
-		return s
-	}
-	for _, q := range []byte{'\'', '"'} {
-		if s[0] == q && s[len(s)-1] == q {
-			return s[1 : len(s)-1]
-		}
-	}
-	return s
-}
-
-func parseVersions(f *os.File, prefix string) (ver Versions, err error) {
-	scanner := bufio.NewScanner(f)
-	for scanner.Scan() {
-		line := strings.SplitN(scanner.Text(), "=", 2)
-		if len(line) != 2 {
-			continue
-		}
-		switch line[0] {
-		case prefix + "VERSION":
-			ver.Version = unquote(line[1])
-		case prefix + "VERSION_ID":
-			ver.VersionID = unquote(line[1])
-		case prefix + "BUILD_ID":
-			ver.BuildID = unquote(line[1])
-		case prefix + "SDK_VERSION":
-			ver.SDKVersion = unquote(line[1])
-		}
-	}
-	if err = scanner.Err(); err != nil {
-		return
-	}
-
-	if ver.VersionID == "" {
-		err = fmt.Errorf("Missing %sVERSION_ID in %s", prefix, f.Name())
-	} else if !strings.HasPrefix(ver.Version, ver.VersionID) {
-		err = fmt.Errorf("Invalid %sVERSION in %s", prefix, f.Name())
-	}
-
-	return
-}
-
-func OSRelease(root string) (ver Versions, err error) {
-	f, err := os.Open(filepath.Join(root, "usr/lib/os-release"))
-	if err != nil {
-		return
-	}
-	defer f.Close()
-
-	return parseVersions(f, "")
-}
-
 func VersionsFromDir(dir string) (ver Versions, err error) {
-	f, err := os.Open(filepath.Join(dir, "version.txt"))
-	if err != nil {
-		return
-	}
-	defer f.Close()
-
-	ver, err = parseVersions(f, "COREOS_")
-	if ver.SDKVersion == "" {
-		err = fmt.Errorf("Missing COREOS_SDK_VERSION in %s", f.Name())
-	}
-
+	err = fmt.Errorf("This API is deprecated")
 	return
 }
-
-func VersionsFromManifest() (Versions, error) {
-	return VersionsFromDir(filepath.Join(RepoRoot(), ".repo", "manifests"))
-}
-
-func versionsFromRemoteRepoMaybeVerify(url, branch string, verify bool) (ver Versions, err error) {
-	// git clone cannot be given a full ref path, instead it explicitly checks
-	// under both refs/heads/<name> and refs/tags/<name>, in that order.
-	if strings.HasPrefix(branch, "refs/") {
-		if strings.HasPrefix(branch, "refs/heads/") {
-			branch = strings.TrimPrefix(branch, "refs/heads/")
-		} else if strings.HasPrefix(branch, "refs/tags/") {
-			branch = strings.TrimPrefix(branch, "refs/tags/")
-		} else {
-			err = fmt.Errorf("SDK version cannot be detected for %q", branch)
-			return
-		}
-	}
-
-	tmp, err := ioutil.TempDir("", "")
-	if err != nil {
-		return
-	}
-	defer os.RemoveAll(tmp)
-
-	clone := exec.Command("git", "clone", "-q", "--depth=1", "--single-branch", "-b", branch, url, tmp)
-	clone.Stderr = os.Stderr
-	if err = clone.Run(); err != nil {
-		err = fmt.Errorf("'git clone %s' failed: %q", branch, err)
-		return
-	}
-
-	if verify {
-		tag := exec.Command("git", "-C", tmp, "tag", "-v", branch)
-		tag.Stderr = os.Stderr
-		if err = tag.Run(); err != nil {
-			err = fmt.Errorf("'git tag --verify %s' failed: %q", branch, err)
-			return
-		}
-	}
-
-	return VersionsFromDir(tmp)
-}
-
-func VersionsFromRemoteRepo(url, branch string) (ver Versions, err error) {
-	return versionsFromRemoteRepoMaybeVerify(url, branch, false)
-}
-
-func VersionsFromSignedRemoteRepo(url, branch string) (ver Versions, err error) {
-	return versionsFromRemoteRepoMaybeVerify(url, branch, true)
-}
-
-func GetDefaultAppId() string {
-	// This is a function in case the id needs to be configurable.
-	return coreosId
-}
-
-const (
-	CoreOSEpoch = 1372636800
-)
-
-// GetCoreOSAge returns the number of days since the CoreOS epoch.
-func GetCoreOSAge() int64 {
-	return int64(time.Since(time.Unix(CoreOSEpoch, 0)) / (86400 * time.Second))
-}