file2lastrev.rb: separate options for Output and VPath

So the `--srcdir` option in this file can override the same option in
`VPath`.

tool/file2lastrev.rb

@@ -28,11 +28,13 @@ vcs = nil
 OptionParser.new {|opts|
   opts.banner << " paths..."
   vcs_options = VCS.define_options(opts)
+  opts.new {@output.def_options(opts)}
   srcdir = nil
   opts.new
   opts.on("--srcdir=PATH", "use PATH as source directory") do |path|
     abort "#{File.basename(Program)}: srcdir is already set" if srcdir
     srcdir = path
+    @output.vpath.add(srcdir)
   end
   opts.on("--changed", "changed rev") do
     self.format = :changed
@@ -53,7 +55,6 @@ OptionParser.new {|opts|
   opts.on("-q", "--suppress_not_found") do
     @suppress_not_found = true
   end
-  @output.def_options(opts)
   opts.order! rescue abort "#{File.basename(Program)}: #{$!}\n#{opts}"
   begin
     vcs = VCS.detect(srcdir || ".", vcs_options, opts.new)

tool/lib/output.rb

@@ -10,6 +10,7 @@ class Output
   end
 
   def def_options(opt)
+    opt.separator("  Output common options:")
     opt.on('-o', '--output=PATH') {|v| @path = v}
     opt.on('-t', '--timestamp[=PATH]') {|v| @timestamp = v || true}
     opt.on('-c', '--[no-]if-change') {|v| @ifchange = v}

tool/lib/vpath.rb

@@ -53,6 +53,7 @@ class VPath
   end
 
   def def_options(opt)
+    opt.separator("  VPath common options:")
     opt.on("-I", "--srcdir=DIR", "add a directory to search path") {|dir|
       @additional << dir
     }
@@ -80,6 +81,10 @@ class VPath
     @list
   end
 
+  def add(path)
+    @additional << path
+  end
+
   def strip(path)
     prefix = list.map {|dir| Regexp.quote(dir)}
     path.sub(/\A#{prefix.join('|')}(?:\/|\z)/, '')