This file is indexed.

/usr/share/doc/texlive-lang-other/README.source is in texlive-lang-other 2016.20170123-5.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
README.source

Packaging TeX Live for Debian is a huge task. Development is done in
a very specific layout and source packages are generated from that.

If you want to know how the *orig.tar.gz* and the *source* packages are 
generated, please check out the Debian TeX Live packaging infrastructure at
  http://anonscm.debian.org/gitweb/?p=debian-tex/texlive-nonbin.git
where you will find a README file explaining everything in detail. Or get it
at
  http://anonscm.debian.org/gitweb/?p=debian-tex/texlive-nonbin.git;a=blob_plain;f=README