cmd/loop: print homedir in help messages as ~

Make the output homedir-independent to facilitate tests.

cmd/loop/default_path_text_test.go

@@ -0,0 +1,82 @@
+package main
+
+import (
+	"errors"
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestDefaultPathText verifies HOME-based path elision behavior used for help
+// defaults without relying on the real environment.
+func TestDefaultPathText(t *testing.T) {
+	sep := string(filepath.Separator)
+	home := filepath.Clean(sep + "home" + sep + "alice")
+
+	homeDir := func() (string, error) { return home, nil }
+
+	tests := []struct {
+		name   string
+		value  string
+		homeFn func() (string, error)
+		want   string
+	}{
+		{
+			name:  "empty value",
+			value: "",
+			homeFn: func() (string, error) {
+				return home, nil
+			},
+			want: "",
+		},
+		{
+			name:   "nil homedir func",
+			value:  home + sep + "data",
+			homeFn: nil,
+			want:   home + sep + "data",
+		},
+		{
+			name:  "homedir error",
+			value: home + sep + "data",
+			homeFn: func() (string, error) {
+				return "", errors.New("homedir error")
+			},
+			want: home + sep + "data",
+		},
+		{
+			name:   "exact home",
+			value:  home,
+			homeFn: homeDir,
+			want:   "~",
+		},
+		{
+			name:   "home prefix",
+			value:  home + sep + "dir" + sep + "file",
+			homeFn: homeDir,
+			want:   "~" + sep + "dir" + sep + "file",
+		},
+		{
+			name:   "non-home path",
+			value:  filepath.Clean(sep + "var" + sep + "tmp"),
+			homeFn: homeDir,
+			want:   filepath.Clean(sep + "var" + sep + "tmp"),
+		},
+		{
+			name:   "prefix but not path segment",
+			value:  home + "x" + sep + "dir",
+			homeFn: homeDir,
+			want:   home + "x" + sep + "dir",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got := defaultPathText(test.value, test.homeFn)
+			require.Equalf(
+				t, test.want, got,
+				"defaultPathText(%q)", test.value,
+			)
+		})
+	}
+}

cmd/loop/main.go

@@ -52,10 +52,11 @@ var (
 	defaultInitiator = "loop-cli"
 
 	loopDirFlag = &cli.StringFlag{
-		Name:    "loopdir",
-		Value:   loopd.LoopDirBase,
-		Usage:   "path to loop's base directory",
-		Sources: cli.EnvVars(envVarLoopDir),
+		Name:        "loopdir",
+		Value:       loopd.LoopDirBase,
+		DefaultText: defaultPathText(loopd.LoopDirBase, os.UserHomeDir),
+		Usage:       "path to loop's base directory",
+		Sources:     cli.EnvVars(envVarLoopDir),
 	}
 	networkFlag = &cli.StringFlag{
 		Name:    "network",
@@ -66,15 +67,21 @@ var (
 	}
 
 	tlsCertFlag = &cli.StringFlag{
-		Name:    "tlscertpath",
-		Usage:   "path to loop's TLS certificate",
-		Value:   loopd.DefaultTLSCertPath,
+		Name:  "tlscertpath",
+		Usage: "path to loop's TLS certificate",
+		Value: loopd.DefaultTLSCertPath,
+		DefaultText: defaultPathText(
+			loopd.DefaultTLSCertPath, os.UserHomeDir,
+		),
 		Sources: cli.EnvVars(envVarTLSCertPath),
 	}
 	macaroonPathFlag = &cli.StringFlag{
-		Name:    "macaroonpath",
-		Usage:   "path to macaroon file",
-		Value:   loopd.DefaultMacaroonPath,
+		Name:  "macaroonpath",
+		Usage: "path to macaroon file",
+		Value: loopd.DefaultMacaroonPath,
+		DefaultText: defaultPathText(
+			loopd.DefaultMacaroonPath, os.UserHomeDir,
+		),
 		Sources: cli.EnvVars(envVarMacaroonPath),
 	}
 	verboseFlag = &cli.BoolFlag{
@@ -132,6 +139,37 @@ const (
 	envVarMacaroonPath = "LOOPCLI_MACAROONPATH"
 )
 
+// defaultPathText returns a help-friendly path string that replaces the user's
+// home directory with "~". The homeDir function is injected so callers can
+// control environment-dependent behavior in tests.
+func defaultPathText(value string, homeDir func() (string, error)) string {
+	if value == "" {
+		return value
+	}
+
+	if homeDir == nil {
+		return value
+	}
+
+	home, err := homeDir()
+	if err != nil || home == "" {
+		return value
+	}
+
+	cleanHome := filepath.Clean(home)
+	cleanValue := filepath.Clean(value)
+	if cleanValue == cleanHome {
+		return "~"
+	}
+
+	prefix := cleanHome + string(filepath.Separator)
+	if suffix, ok := strings.CutPrefix(cleanValue, prefix); ok {
+		return "~" + string(filepath.Separator) + suffix
+	}
+
+	return value
+}
+
 func printJSON(resp any) {
 	b, err := json.Marshal(resp)
 	if err != nil {