test: refactor a single maybeCloneLinguist() impl

internal/tests/utils.go

@@ -0,0 +1,48 @@
+package tests
+
+import (
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+)
+
+// Re-used by the packages: enry (test), enry (benchmark) and code-generator (test).
+// Does not rely on testify, panics on errors so that there always is a trace to the caller.
+func MaybeCloneLinguist(envVar, url, commit string) (string, bool, error) {
+	var err error
+	linguistTmpDir := os.Getenv(envVar)
+	isCleanupNeeded := false
+	isLinguistCloned := linguistTmpDir != ""
+	if !isLinguistCloned {
+		linguistTmpDir, err = ioutil.TempDir("", "linguist-")
+		if err != nil {
+			return "", false, err
+		}
+
+		isCleanupNeeded = true
+		cmd := exec.Command("git", "clone", "--depth", "100", url, linguistTmpDir)
+		if err := cmd.Run(); err != nil {
+			panic(fmt.Errorf("%s: %w", cmd.String(), err))
+		}
+	}
+
+	cwd, err := os.Getwd()
+	if err != nil {
+		panic(err)
+	}
+
+	if err = os.Chdir(linguistTmpDir); err != nil {
+		panic(err)
+	}
+
+	cmd := exec.Command("git", "checkout", commit)
+	if err := cmd.Run(); err != nil {
+		panic(fmt.Errorf("%s: %w", cmd.String(), err))
+	}
+
+	if err = os.Chdir(cwd); err != nil {
+		panic(fmt.Errorf("%s: %w", cmd.String(), err))
+	}
+	return linguistTmpDir, isCleanupNeeded, nil
+}