Question about defined music functions

[James]

Hello,

Can I assume (dangerous ground I know) that if I look in 
ly/music-functions-init.ly and see an entry that has the form

someString =
 #(define-music-function ...

That this is always a command in the form

\someString

That a user can directly in a .ly file (if you see what I mean/).

I ask because if I look (for example) at this checkin

http://git.savannah.gnu.org/gitweb/?p=lilypond.git;a=commit;h=3b65aea88185c2ce92b1a905e0535d7d4c60d71a

I can see that the ly/music-functions-init.ly file shows

+magnifyMusic =
+#(define-music-function ....

but if I look at this check-in

http://git.savannah.gnu.org/gitweb/?p=lilypond.git;a=commit;h=d3e856b31301bc6e67a13118ad432d22897d9f8b

The new function \justify-line seems to only touch the 
scm/define-markup-commands.scm  file and nothing is added to 
ly/music-functions-init.ly

Regards

James