Add shell completion

cli_test.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestCompletionCommandGeneratesSupportedShells(t *testing.T) {
+	for _, shell := range completionShells {
+		t.Run(shell, func(t *testing.T) {
+			var output bytes.Buffer
+			handled, err := handleCompletionCommand([]string{"completion", shell}, &output)
+			if err != nil {
+				t.Fatal(err)
+			}
+			if !handled || output.Len() == 0 ||
+				!strings.Contains(output.String(), "diple") {
+				t.Fatalf("completion output = %q, handled=%t", output.String(), handled)
+			}
+		})
+	}
+}
+
+func TestZshCompletionRegistersWithoutCallingCompletionFunction(t *testing.T) {
+	var output bytes.Buffer
+	handled, err := handleCompletionCommand([]string{"completion", "zsh"}, &output)
+	if err != nil {
+		t.Fatal(err)
+	}
+	script := output.String()
+	if !handled || !strings.Contains(script, "compdef _diple diple") {
+		t.Fatalf("Zsh completion does not register _diple:\n%s", script)
+	}
+	if strings.Contains(script, `_diple "$@"`) {
+		t.Fatalf("Zsh completion invokes _diple while being sourced:\n%s", script)
+	}
+}
+
+func TestCompletionCommandRejectsUnknownShell(t *testing.T) {
+	var output bytes.Buffer
+	handled, err := handleCompletionCommand(
+		[]string{"completion", "powershell"}, &output,
+	)
+	if !handled || err == nil || !strings.Contains(err.Error(), "unsupported shell") {
+		t.Fatalf("handled=%t error=%v", handled, err)
+	}
+}
+
+func TestCompletionCommandDoesNotClaimNormalInvocation(t *testing.T) {
+	handled, err := handleCompletionCommand([]string{"--repo", "owner/repo"}, &bytes.Buffer{})
+	if handled || err != nil {
+		t.Fatalf("handled=%t error=%v", handled, err)
+	}
+}
+
+func TestCLIHelpIsGroupedAndActionable(t *testing.T) {
+	var output bytes.Buffer
+	writeCLIHelp(&output, defaultConfig(), "/tmp/diple/config.toml")
+	help := output.String()
+	for _, expected := range []string{
+		"Usage:",
+		"Pull-request selection:",
+		"GitHub and refresh:",
+		"Appearance and navigation:",
+		"Local state:",
+		"diple completion <bash|zsh|fish>",
+		"--repo OWNER/REPOSITORY",
+		"--cache=false",
+		"gh auth login",
+		"/tmp/diple/config.toml",
+	} {
+		if !strings.Contains(help, expected) {
+			t.Fatalf("help does not contain %q:\n%s", expected, help)
+		}
+	}
+}