‘file-append’

[Ludovic Courtès]

Hello Guix!

As a resolution to <http://bugs.gnu.org/20067>, (guix gexp) provides a
new construct, ‘file-append’, which can be used to express the
concatenation of file name components.

Previously, we would typically write:

  #~(string-append #$coreutils "/bin/uname")

which would lead to an sexp like:

  (string-append "/gnu/store/…-coreutils-8.25" "/bin/uname")

Now we can still do that, but we can also write:

  (file-append coreutils "/bin/uname")

which leads to:

  "/gnu/store/…-coreutils-8.25/bin/uname"

This is necessary in some situations, such as that of #20067, and it
saves a little bit of typing and doesn’t cost much.  In
9e41130b14ad32c4e1fa756f95d806703056cb60 I converted a bunch of GuixSD
modules to this new style (apologies to those who will experience merge
conflicts ;-)).

Comments welcome!

Ludo’.