Some .Hugo variables in 0.16 are empty

The Hugo variables page lists .Hugo.BuildDate and .Hugo.CommitHash as available, but they’re showing up empty when I use them.

 <dl>
  <dt><dfn>.Hugo</dfn></dt> <dd>{{.Hugo}}</dd>
  <dt><dfn>.Hugo.BuildDate</dfn></dt> <dd>{{.Hugo.BuildDate}}</dd>
  <dt><dfn>.Hugo.CommitHash</dfn></dt> <dd>{{.Hugo.CommitHash}}</dd>
  <dt><dfn>.Hugo.Version</dfn></dt> <dd>{{.Hugo.Version}}</dd>
 </dl>

Renders to:

 <dl>
  <dt><dfn>.Hugo</dfn></dt> <dd>{0.16-DEV &lt;meta name=&#34;generator&#34; content=&#34;Hugo 0.16-DEV&#34; /&gt;  }</dd>
  <dt><dfn>.Hugo.BuildDate</dfn></dt> <dd></dd>
  <dt><dfn>.Hugo.CommitHash</dfn></dt> <dd></dd>
  <dt><dfn>.Hugo.Version</dfn></dt> <dd>0.16-DEV</dd>
 </dl>

I don’t understand why .BuildDate and .CommitHash are empty. I built from spf13/master:

$ hugo version
Hugo Static Site Generator v0.16-DEV BuildDate: 2015-11-27T02:35:19-06:00

the instructions on how to set those are in the readme.md file. If you use make it will just work as well.

I also notice the same (only .Hugo.BuildDate and .Hugo.CommitHash are empty). I failed to find instructions in README.md.

Update: Running make install fixes this.

If not using make install, one can do

PACKAGE="github.com/spf13/hugo"
go install -v -ldflags "-X ${PACKAGE}/hugolib.CommitHash=`git rev-parse --short HEAD 2>/dev/null` -X ${PACKAGE}/hugolib.BuildDate=`date +%FT%T%z`" ${PACKAGE}