refactor: rename setup.GetRelease to readOrFetchRelease

The function is moved back to the `main` package and is declared in
cmd/chisel/helpers.go file.

cmd/chisel/cmd_cut.go

@@ -49,7 +49,7 @@ func (cmd *cmdCut) Execute(args []string) error {
 		sliceKeys[i] = sliceKey
 	}
 
-	release, _, err := setup.GetRelease(cmd.Release)
+	release, _, err := readOrFetchRelease(cmd.Release)
 	if err != nil {
 		return err
 	}

cmd/chisel/cmd_find.go

@@ -49,7 +49,7 @@ func (cmd *cmdFind) Execute(args []string) error {
 		return fmt.Errorf("no search term specified")
 	}
 
-	release, releaseLabel, err := setup.GetRelease(cmd.Release)
+	release, releaseLabel, err := readOrFetchRelease(cmd.Release)
 	if err != nil {
 		return err
 	}

cmd/chisel/helpers.go

@@ -0,0 +1,73 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+
+	"github.com/canonical/chisel/internal/setup"
+)
+
+// TODO These need testing
+
+var releaseExp = regexp.MustCompile(`^([a-z](?:-?[a-z0-9]){2,})-([0-9]+(?:\.?[0-9])+)$`)
+
+func parseReleaseInfo(release string) (label, version string, err error) {
+	match := releaseExp.FindStringSubmatch(release)
+	if match == nil {
+		return "", "", fmt.Errorf("invalid release reference: %q", release)
+	}
+	return match[1], match[2], nil
+}
+
+func readReleaseInfo() (label, version string, err error) {
+	data, err := os.ReadFile("/etc/lsb-release")
+	if err == nil {
+		const labelPrefix = "DISTRIB_ID="
+		const versionPrefix = "DISTRIB_RELEASE="
+		for _, line := range strings.Split(string(data), "\n") {
+			switch {
+			case strings.HasPrefix(line, labelPrefix):
+				label = strings.ToLower(line[len(labelPrefix):])
+			case strings.HasPrefix(line, versionPrefix):
+				version = line[len(versionPrefix):]
+			}
+			if label != "" && version != "" {
+				return label, version, nil
+			}
+		}
+	}
+	return "", "", fmt.Errorf("cannot infer release via /etc/lsb-release, see the --release option")
+}
+
+// readOrFetchRelease takes a release branch name or a release directory path.
+// It fetches or reads the chisel-release depending on the nature of input and
+// returns the release and release label.
+// If the input is empty, it tries to read the release label from the host
+// system and fetch the chisel-release accordingly.
+func readOrFetchRelease(releaseStr string) (release *setup.Release, releaseLabel string, err error) {
+	if strings.Contains(releaseStr, "/") {
+		release, err = setup.ReadRelease(releaseStr)
+		releaseLabel = releaseStr
+	} else {
+		var label, version string
+		if releaseStr == "" {
+			label, version, err = readReleaseInfo()
+		} else {
+			label, version, err = parseReleaseInfo(releaseStr)
+		}
+		if err != nil {
+			return nil, "", err
+		}
+		release, err = setup.FetchRelease(&setup.FetchOptions{
+			Label:   label,
+			Version: version,
+		})
+		releaseLabel = label + "-" + version
+	}
+	if err != nil {
+		return nil, "", err
+	}
+	return release, releaseLabel, nil
+}

internal/setup/setup.go

@@ -623,63 +623,3 @@ func Select(release *Release, slices []SliceKey) (*Selection, error) {
 
 	return selection, nil
 }
-
-// TODO These need testing
-
-var releaseExp = regexp.MustCompile(`^([a-z](?:-?[a-z0-9]){2,})-([0-9]+(?:\.?[0-9])+)$`)
-
-func parseReleaseInfo(release string) (label, version string, err error) {
-	match := releaseExp.FindStringSubmatch(release)
-	if match == nil {
-		return "", "", fmt.Errorf("invalid release reference: %q", release)
-	}
-	return match[1], match[2], nil
-}
-
-func readReleaseInfo() (label, version string, err error) {
-	data, err := os.ReadFile("/etc/lsb-release")
-	if err == nil {
-		const labelPrefix = "DISTRIB_ID="
-		const versionPrefix = "DISTRIB_RELEASE="
-		for _, line := range strings.Split(string(data), "\n") {
-			switch {
-			case strings.HasPrefix(line, labelPrefix):
-				label = strings.ToLower(line[len(labelPrefix):])
-			case strings.HasPrefix(line, versionPrefix):
-				version = line[len(versionPrefix):]
-			}
-			if label != "" && version != "" {
-				return label, version, nil
-			}
-		}
-	}
-	return "", "", fmt.Errorf("cannot infer release via /etc/lsb-release, see the --release option")
-}
-
-// GetRelease returns the release and release label (e.g. ubuntu-22.04 or
-// /path/to/release/dir/ if a directory was passed as input).
-func GetRelease(releaseStr string) (release *Release, releaseLabel string, err error) {
-	if strings.Contains(releaseStr, "/") {
-		release, err = ReadRelease(releaseStr)
-		releaseLabel = releaseStr
-	} else {
-		var label, version string
-		if releaseStr == "" {
-			label, version, err = readReleaseInfo()
-		} else {
-			label, version, err = parseReleaseInfo(releaseStr)
-		}
-		if err != nil {
-			return nil, "", err
-		}
-		release, err = FetchRelease(&FetchOptions{
-			Label:   label,
-			Version: version,
-		})
-		releaseLabel = label + "-" + version
-	}
-	if err != nil {
-		return nil, "", err
-	}
-	return release, releaseLabel, nil
-}