add go-diff diagnostic program

Author: sqs

cmd/go-diff/go-diff.go

@@ -0,0 +1,77 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+
+	"sourcegraph.com/sourcegraph/go-diff/diff"
+)
+
+// A diagnostic program to aid in debugging diff parsing or printing
+// errors.
+
+const stdin = "<stdin>"
+
+var (
+	diffPath = flag.String("f", stdin, "filename of diff (default: stdin)")
+	fileIdx  = flag.Int("i", -1, "if >= 0, only print and report errors from the i'th file (0-indexed)")
+)
+
+func main() {
+	log.SetFlags(0)
+	flag.Parse()
+
+	var diffFile *os.File
+	if *diffPath == stdin {
+		diffFile = os.Stdin
+	} else {
+		var err error
+		diffFile, err = os.Open(*diffPath)
+		if err != nil {
+			log.Fatal(err)
+		}
+	}
+	defer diffFile.Close()
+
+	r := diff.NewMultiFileDiffReader(diffFile)
+	for i := 0; ; i++ {
+		report := (*fileIdx == -1) || i == *fileIdx // true if -i==-1 or if this is the i'th file
+
+		label := fmt.Sprintf("file(%d)", i)
+		fdiff, err := r.ReadFile()
+		if fdiff != nil {
+			label = fmt.Sprintf("orig(%s) new(%s)", fdiff.OrigName, fdiff.NewName)
+		}
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			if report {
+				log.Fatalf("err read %s: %s", label, err)
+			} else {
+				continue
+			}
+		}
+
+		if report {
+			log.Printf("ok read: %s", label)
+		}
+
+		out, err := diff.PrintFileDiff(fdiff)
+		if err != nil {
+			if report {
+				log.Fatalf("err print %s: %s", label, err)
+			} else {
+				continue
+			}
+		}
+		if report {
+			if _, err := os.Stdout.Write(out); err != nil {
+				log.Fatal(err)
+			}
+		}
+	}
+}