acc: add -useversion flag for testing older versions (#3404)

## Changes
New flag -useversion that downloads old version and uses it to run
acceptance tests.

## Why
Allows to quickly find out if a given behaviour is a regression.

## Tests
Manually. For example, run current test suite on most recent release:
`go test ./acceptance -useversion 0.263.0`

Author: denik

acceptance/acceptance_test.go

@@ -1,6 +1,7 @@
 package acceptance_test
 
 import (
+	"archive/zip"
 	"bufio"
 	"context"
 	"encoding/base32"
@@ -44,6 +45,7 @@ var (
 	LogRequests bool
 	LogConfig   bool
 	SkipLocal   bool
+	UseVersion  string
 )
 
 // In order to debug CLI running under acceptance test, search for TestInprocessMode and update
@@ -64,6 +66,7 @@ func init() {
 	flag.BoolVar(&LogRequests, "logrequests", false, "Log request and responses from testserver")
 	flag.BoolVar(&LogConfig, "logconfig", false, "Log merged for each test case")
 	flag.BoolVar(&SkipLocal, "skiplocal", false, "Skip tests that are enabled to run on Local")
+	flag.StringVar(&UseVersion, "useversion", "", "Download previously released version of CLI and use it to run the tests")
 }
 
 const (
@@ -166,7 +169,11 @@ func testAccept(t *testing.T, inprocessMode bool, singleTest string) int {
 		t.Setenv("CMD_SERVER_URL", cmdServer.URL)
 		execPath = filepath.Join(cwd, "bin", "callserver.py")
 	} else {
-		execPath = BuildCLI(t, buildDir, coverDir)
+		if UseVersion != "" {
+			execPath = DownloadCLI(t, buildDir, UseVersion)
+		} else {
+			execPath = BuildCLI(t, buildDir, coverDir)
+		}
 	}
 
 	BuildYamlfmt(t)
@@ -827,6 +834,83 @@ func BuildCLI(t *testing.T, buildDir, coverDir string) string {
 	return execPath
 }
 
+// DownloadCLI downloads a released CLI binary archive for the given version,
+// extracts the executable, and returns its path.
+func DownloadCLI(t *testing.T, buildDir, version string) string {
+	// Prepare target directory for this version
+	versionDir := filepath.Join(buildDir, version)
+	require.NoError(t, os.MkdirAll(versionDir, 0o755))
+
+	execName := "databricks"
+	if runtime.GOOS == "windows" {
+		execName += ".exe"
+	}
+	execPath := filepath.Join(versionDir, execName)
+
+	// If already downloaded, reuse
+	if _, err := os.Stat(execPath); err == nil {
+		return execPath
+	}
+
+	osName := runtime.GOOS
+	archName := runtime.GOARCH
+
+	// Compose archive name per release naming scheme
+	archiveName := fmt.Sprintf("databricks_cli_%s_%s_%s.zip", version, osName, archName)
+	url := fmt.Sprintf("https://github.com/databricks/cli/releases/download/v%s/%s", version, archiveName)
+	zipPath := filepath.Join(versionDir, archiveName)
+
+	downloadToFile(t, url, zipPath)
+	extractFileFromZip(t, zipPath, execName, versionDir)
+
+	return execPath
+}
+
+// downloadToFile downloads contents from url into the given destination path
+func downloadToFile(t *testing.T, url, destPath string) {
+	require.NoError(t, os.MkdirAll(filepath.Dir(destPath), 0o755))
+	out, err := os.Create(destPath)
+	require.NoError(t, err)
+	defer out.Close()
+
+	resp, err := http.Get(url)
+	require.NoError(t, err)
+	defer resp.Body.Close()
+	require.Equal(t, http.StatusOK, resp.StatusCode, "failed to download %s: %s", url, resp.Status)
+
+	_, err = io.Copy(out, resp.Body)
+	require.NoError(t, err)
+}
+
+// extractFileFromZip finds a file by name inside a zip archive and writes it
+// into destDir using the file's base name. Fails the test if not found.
+func extractFileFromZip(t *testing.T, zipPath, fileName, destDir string) {
+	r, err := zip.OpenReader(zipPath)
+	require.NoError(t, err)
+	defer r.Close()
+
+	targetBase := filepath.Base(fileName)
+	destPath := filepath.Join(destDir, targetBase)
+	var found bool
+	for _, f := range r.File {
+		if filepath.Base(f.Name) != targetBase {
+			continue
+		}
+		rc, err := f.Open()
+		require.NoError(t, err)
+		defer rc.Close()
+
+		out, err := os.OpenFile(destPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0o755)
+		require.NoError(t, err)
+		_, err = io.Copy(out, rc)
+		_ = out.Close()
+		require.NoError(t, err)
+		found = true
+		break
+	}
+	require.True(t, found, "file %s not found in archive %s", targetBase, zipPath)
+}
+
 func copyFile(src, dst string) error {
 	in, err := os.Open(src)
 	if err != nil {