Functionalize library clone folder deletion code

Both the `libraries-repository-engine remove` and `libraries-repository-engine modify --repo-url` commands delete the
library's "Git clone folder". Previously, the code for doing this was repeated verbatim for each command.

At the time the code was written, this was considered reasonable since it was not a lot of code and the architectural
structure of the module does not provide an obvious location for a shared function containing that code. However, it is
now planned to add additional code, which tips the balance toward a function.

This also enables increasing the unit test coverage of the code.

Author: per1234

internal/command/modify/modify.go

@@ -164,18 +164,9 @@ func modifyRepositoryURL(newRepositoryURL string) error {
 	fmt.Printf("Changing URL of library %s from %s to %s\n", libraryName, oldRepositoryURL, newRepositoryURL)
 
 	// Remove the library Git clone folder. It will be cloned from the new URL on the next sync.
-	libraryRegistration := libraries.Repo{URL: libraryData.Repository}
-	gitCloneSubfolder, err := libraryRegistration.AsFolder()
-	if err != nil {
+	if err := libraries.BackupAndDeleteGitClone(config, &libraries.Repo{URL: libraryData.Repository}); err != nil {
 		return err
 	}
-	gitClonePath := paths.New(config.GitClonesFolder, gitCloneSubfolder)
-	if err := backup.Backup(gitClonePath); err != nil {
-		return fmt.Errorf("While backing up library's Git clone: %w", err)
-	}
-	if err := gitClonePath.RemoveAll(); err != nil {
-		return fmt.Errorf("While removing library's Git clone: %w", err)
-	}
 
 	// Update the library repository URL in the database.
 	libraryData.Repository = newRepositoryURL

internal/command/remove/remove.go

@@ -160,18 +160,9 @@ func removeLibrary(libraryName string) error {
 	}
 
 	// Remove the library Git clone folder.
-	libraryRegistration := libraries.Repo{URL: libraryData.Repository}
-	gitCloneSubfolder, err := libraryRegistration.AsFolder()
-	if err != nil {
+	if err := libraries.BackupAndDeleteGitClone(config, &libraries.Repo{URL: libraryData.Repository}); err != nil {
 		return err
 	}
-	gitClonePath := paths.New(config.GitClonesFolder, gitCloneSubfolder)
-	if err := backup.Backup(gitClonePath); err != nil {
-		return fmt.Errorf("While backing up library's Git clone: %w", err)
-	}
-	if err := gitClonePath.RemoveAll(); err != nil {
-		return fmt.Errorf("While removing library Git clone: %s", err)
-	}
 
 	return nil
 }

internal/libraries/repoclone.go

@@ -28,6 +28,9 @@ import (
 	"os"
 	"path/filepath"
 
+	"github.com/arduino/go-paths-helper"
+	"github.com/arduino/libraries-repository-engine/internal/backup"
+	"github.com/arduino/libraries-repository-engine/internal/configuration"
 	"github.com/arduino/libraries-repository-engine/internal/libraries/db"
 
 	"fmt"
@@ -134,3 +137,21 @@ func UpdateLibrary(release *db.Release, repoURL string, libraryDb *db.DB) error
 
 	return nil
 }
+
+// BackupAndDeleteGitClone backs up and then deletes the library's Git clone folder.
+func BackupAndDeleteGitClone(config *configuration.Config, repoMeta *Repo) error {
+	gitCloneSubfolder, err := repoMeta.AsFolder()
+	if err != nil {
+		return err
+	}
+	gitClonePath := paths.New(config.GitClonesFolder, gitCloneSubfolder)
+
+	if err := backup.Backup(gitClonePath); err != nil {
+		return fmt.Errorf("While backing up library's Git clone: %w", err)
+	}
+	if err := gitClonePath.RemoveAll(); err != nil {
+		return fmt.Errorf("While removing library Git clone: %s", err)
+	}
+
+	return nil
+}

internal/libraries/repoclone_test.go

@@ -28,6 +28,10 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/arduino/go-paths-helper"
+	"github.com/arduino/libraries-repository-engine/internal/backup"
+	"github.com/arduino/libraries-repository-engine/internal/configuration"
+	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
@@ -48,3 +52,38 @@ func TestCloneRepos(t *testing.T) {
 	_, err = os.Stat(repo.FolderPath)
 	require.NoError(t, err)
 }
+
+func TestBackupAndDeleteGitClone(t *testing.T) {
+	var err error
+
+	gitClonesFolder, err := paths.MkTempDir("", "libraries-test-testbackupanddeletegitclone")
+	require.NoError(t, err)
+	config := configuration.Config{
+		GitClonesFolder: gitClonesFolder.String(),
+	}
+	repoMeta := Repo{
+		URL: "https://github.com/Foo/Bar.git",
+	}
+
+	assert.Error(t, BackupAndDeleteGitClone(&config, &repoMeta), "Error if library clone folder did not exist.")
+
+	gitCloneSubfolder, err := repoMeta.AsFolder()
+	require.NoError(t, err)
+	gitClonePath := paths.New(config.GitClonesFolder, gitCloneSubfolder)
+	err = gitClonePath.MkdirAll()
+	require.NoError(t, err)
+
+	assert.Nil(t, BackupAndDeleteGitClone(&config, &repoMeta), "Return nil if library clone folder did exist.")
+
+	exist, err := gitClonePath.ExistCheck()
+	require.NoError(t, err)
+
+	assert.False(t, exist, "Library clone folder was deleted.")
+
+	err = backup.Restore()
+	require.NoError(t, err)
+	exist, err = gitClonePath.ExistCheck()
+	require.NoError(t, err)
+
+	assert.True(t, exist, "Library clone folder was backed up.")
+}