Use deterministic date for man pages

cmd/restic/cmd_manpage.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"os"
+	"time"
 
 	"github.com/restic/restic/internal/errors"
 	"github.com/spf13/cobra"
@@ -31,10 +32,17 @@ func init() {
 }
 
 func runManpage(cmd *cobra.Command, args []string) error {
+	// use a fixed date for the man pages so that generating them is deterministic
+	date, err := time.Parse("Jan 2006", "Jan 2017")
+	if err != nil {
+		return err
+	}
+
 	header := &doc.GenManHeader{
 		Title:   "restic backup",
 		Section: "1",
 		Source:  "generated by `restic manpage`",
+		Date:    &date,
 	}
 
 	dir := manpageOpts.OutputDir