clientupdate: remove Arch support (#9081)

An Arch Linux maintainer asked us to not implement "tailscale update" on
Arch-based distros:
https://github.com/tailscale/tailscale/issues/6995#issuecomment-1687080106

Return an error to the user if they try to run "tailscale update".

Updates #6995

Signed-off-by: Andrew Lytvynov <awly@tailscale.com>

clientupdate/clientupdate.go

@@ -403,61 +403,12 @@ func updateDebianAptSourcesListBytes(was []byte, dstTrack string) (newContent []
 	return buf.Bytes(), nil
 }
 
-func (up *updater) updateArchLike() (err error) {
+func (up *updater) updateArchLike() error {
-	if up.Version != "" {
+	// Arch maintainer asked us not to implement "tailscale update" or
-		return errors.New("installing a specific version on Arch-based distros is not supported")
+	// auto-updates on Arch-based distros:
-	}
+	// https://github.com/tailscale/tailscale/issues/6995#issuecomment-1687080106
-	if err := requireRoot(); err != nil {
+	return errors.New(`individual package updates are not supported on Arch-based distros, only full-system updates are: https://wiki.archlinux.org/title/System_maintenance#Partial_upgrades_are_unsupported.
-		return err
+you can use "pacman --sync --refresh --sysupgrade" or "pacman -Syu" to upgrade the system, including Tailscale.`)
-	}
-
-	defer func() {
-		if err != nil {
-			err = fmt.Errorf(`%w; you can try updating using "pacman --sync --refresh tailscale"`, err)
-		}
-	}()
-
-	out, err := exec.Command("pacman", "--sync", "--refresh", "--info", "tailscale").CombinedOutput()
-	if err != nil {
-		return fmt.Errorf("failed checking pacman for latest tailscale version: %w, output: %q", err, out)
-	}
-	ver, err := parsePacmanVersion(out)
-	if err != nil {
-		return err
-	}
-	if !up.confirm(ver) {
-		return nil
-	}
-
-	cmd := exec.Command("pacman", "--sync", "--noconfirm", "tailscale")
-	cmd.Stdout = os.Stdout
-	cmd.Stderr = os.Stderr
-	if err := cmd.Run(); err != nil {
-		return fmt.Errorf("failed tailscale update using pacman: %w", err)
-	}
-	return nil
-}
-
-func parsePacmanVersion(out []byte) (string, error) {
-	for _, line := range strings.Split(string(out), "\n") {
-		// The line we're looking for looks like this:
-		// Version         : 1.44.2-1
-		if !strings.HasPrefix(line, "Version") {
-			continue
-		}
-		parts := strings.SplitN(line, ":", 2)
-		if len(parts) != 2 {
-			return "", fmt.Errorf("version output from pacman is malformed: %q, cannot determine upgrade version", line)
-		}
-		ver := strings.TrimSpace(parts[1])
-		// Trim the Arch patch version.
-		ver = strings.Split(ver, "-")[0]
-		if ver == "" {
-			return "", fmt.Errorf("version output from pacman is malformed: %q, cannot determine upgrade version", line)
-		}
-		return ver, nil
-	}
-	return "", fmt.Errorf("could not find latest version of tailscale via pacman")
 }
 
 const yumRepoConfigFile = "/etc/yum.repos.d/tailscale.repo"

clientupdate/clientupdate_test.go

@@ -157,108 +157,6 @@ func TestParseSoftwareupdateList(t *testing.T) {
 	}
 }
 
-func TestParsePacmanVersion(t *testing.T) {
-	tests := []struct {
-		desc    string
-		out     string
-		want    string
-		wantErr bool
-	}{
-		{
-			desc: "valid version",
-			out: `
-:: Synchronizing package databases...
- endeavouros is up to date
- core is up to date
- extra is up to date
- multilib is up to date
-Repository      : extra
-Name            : tailscale
-Version         : 1.44.2-1
-Description     : A mesh VPN that makes it easy to connect your devices, wherever they are.
-Architecture    : x86_64
-URL             : https://tailscale.com
-Licenses        : MIT
-Groups          : None
-Provides        : None
-Depends On      : glibc
-Optional Deps   : None
-Conflicts With  : None
-Replaces        : None
-Download Size   : 7.98 MiB
-Installed Size  : 32.47 MiB
-Packager        : Christian Heusel <gromit@archlinux.org>
-Build Date      : Tue 18 Jul 2023 12:28:37 PM PDT
-Validated By    : MD5 Sum  SHA-256 Sum  Signature
-`,
-			want: "1.44.2",
-		},
-		{
-			desc: "version without Arch patch number",
-			out: `
-... snip ...
-Name            : tailscale
-Version         : 1.44.2
-Description     : A mesh VPN that makes it easy to connect your devices, wherever they are.
-... snip ...
-`,
-			want: "1.44.2",
-		},
-		{
-			desc: "missing version",
-			out: `
-... snip ...
-Name            : tailscale
-Description     : A mesh VPN that makes it easy to connect your devices, wherever they are.
-... snip ...
-`,
-			wantErr: true,
-		},
-		{
-			desc: "empty version",
-			out: `
-... snip ...
-Name            : tailscale
-Version         :
-Description     : A mesh VPN that makes it easy to connect your devices, wherever they are.
-... snip ...
-`,
-			wantErr: true,
-		},
-		{
-			desc:    "empty input",
-			out:     "",
-			wantErr: true,
-		},
-		{
-			desc: "sneaky version in description",
-			out: `
-... snip ...
-Name            : tailscale
-Description     : A mesh VPN that makes it easy to connect your devices, wherever they are. Version : 1.2.3
-Version         : 1.44.2
-... snip ...
-`,
-			want: "1.44.2",
-		},
-	}
-
-	for _, tt := range tests {
-		t.Run(tt.desc, func(t *testing.T) {
-			got, err := parsePacmanVersion([]byte(tt.out))
-			if err == nil && tt.wantErr {
-				t.Fatalf("got nil error and version %q, want non-nil error", got)
-			}
-			if err != nil && !tt.wantErr {
-				t.Fatalf("got error: %q, want nil", err)
-			}
-			if got != tt.want {
-				t.Fatalf("got version: %q, want %q", got, tt.want)
-			}
-		})
-	}
-}
-
 func TestUpdateYUMRepoTrack(t *testing.T) {
 	tests := []struct {
 		desc    string