backup: Do not print hostname in help text

This is necessary so that the manpage generation is deterministic and we
can test if the man pages are up to date when the CI tests run.

cmd/restic/cmd_backup.go

@@ -27,6 +27,16 @@ var cmdBackup = &cobra.Command{
 The "backup" command creates a new snapshot and saves the files and directories
 given as the arguments.
 `,
+	PreRun: func(cmd *cobra.Command, args []string) {
+		if backupOptions.Hostname == "" {
+			hostname, err := os.Hostname()
+			if err != nil {
+				debug.Log("os.Hostname() returned err: %v", err)
+				return
+			}
+			backupOptions.Hostname = hostname
+		}
+	},
 	RunE: func(cmd *cobra.Command, args []string) error {
 		if backupOptions.Stdin && backupOptions.FilesFrom == "-" {
 			return errors.Fatal("cannot use both `--stdin` and `--files-from -`")
@@ -59,12 +69,6 @@ var backupOptions BackupOptions
 func init() {
 	cmdRoot.AddCommand(cmdBackup)
 
-	hostname, err := os.Hostname()
-	if err != nil {
-		debug.Log("os.Hostname() returned err: %v", err)
-		hostname = ""
-	}
-
 	f := cmdBackup.Flags()
 	f.StringVar(&backupOptions.Parent, "parent", "", "use this parent snapshot (default: last snapshot in the repo that has the same target files/directories)")
 	f.BoolVarP(&backupOptions.Force, "force", "f", false, `force re-reading the target files/directories (overrides the "parent" flag)`)
@@ -74,7 +78,7 @@ func init() {
 	f.BoolVar(&backupOptions.Stdin, "stdin", false, "read backup from stdin")
 	f.StringVar(&backupOptions.StdinFilename, "stdin-filename", "stdin", "file name to use when reading from stdin")
 	f.StringArrayVar(&backupOptions.Tags, "tag", nil, "add a `tag` for the new snapshot (can be specified multiple times)")
-	f.StringVar(&backupOptions.Hostname, "hostname", hostname, "set the `hostname` for the snapshot manually")
+	f.StringVar(&backupOptions.Hostname, "hostname", "", "set the `hostname` for the snapshot manually")
 	f.StringVar(&backupOptions.FilesFrom, "files-from", "", "read the files to backup from file (can be combined with file args)")
 }
 

doc/man/restic-backup.1

@@ -41,7 +41,7 @@ given as the arguments.
     help for backup
 
 .PP
-\fB\-\-hostname\fP="mopped"
+\fB\-\-hostname\fP=""
     set the \fB\fChostname\fR for the snapshot manually
 
 .PP