diff kitten: Allow diffing named pipes

Fixes #8597

kittens/diff/main.go

@@ -6,6 +6,7 @@ import (
 	"archive/tar"
 	"bytes"
 	"fmt"
+	"io"
 	"io/fs"
 	"os"
 	"os/exec"
@@ -43,9 +44,33 @@ func isdir(path string) bool {
 	return false
 }
 
-func exists(path string) bool {
-	_, err := os.Stat(path)
-	return err == nil
+var temp_files []string
+
+func resolve_path(path string) (ans string, err error) {
+	var s fs.FileInfo
+	if s, err = os.Stat(path); err != nil {
+		return
+	} else {
+		if s.Mode()&fs.ModeNamedPipe != 0 {
+			var src, dest *os.File
+			if src, err = os.Open(path); err != nil {
+				return
+			}
+			defer src.Close()
+			if dest, err = os.CreateTemp("", fmt.Sprintf("*-pipe-%d", len(temp_files)+1)); err != nil {
+				return
+			}
+			defer dest.Close()
+			temp_files = append(temp_files, dest.Name())
+			if _, err = io.Copy(dest, src); err != nil {
+				return
+			}
+			return dest.Name(), nil
+
+		} else {
+			return path, nil
+		}
+	}
 }
 
 func get_ssh_file(hostname, rpath string) (string, error) {
@@ -136,11 +161,16 @@ func main(_ *cli.Command, opts_ *Options, args []string) (rc int, err error) {
 	if isdir(left) != isdir(right) {
 		return 1, fmt.Errorf("The items to be diffed should both be either directories or files. Comparing a directory to a file is not valid.'")
 	}
-	if !exists(left) {
-		return 1, fmt.Errorf("%s does not exist", left)
+	defer func() {
+		for _, path := range temp_files {
+			os.Remove(path)
+		}
+	}()
+	if left, err = resolve_path(left); err != nil {
+		return 1, err
 	}
-	if !exists(right) {
-		return 1, fmt.Errorf("%s does not exist", right)
+	if right, err = resolve_path(right); err != nil {
+		return 1, err
 	}
 	lp, err = loop.New()
 	loop.MouseTrackingMode(lp, loop.BUTTONS_AND_DRAG_MOUSE_TRACKING)