gnu: texlive-latex-filecontents: Fix package definition.

* gnu/packages/tex.scm (texlive-latex-filecontents)[arguments]: Generate from
source.

gnu/packages/tex.scm

@@ -3340,29 +3340,34 @@ a process to convert the EPS to PDF, using the script @command{epstopdf}.")
 (define-deprecated-package texlive-latex-epstopdf-pkg texlive-epstopdf-pkg)
 
 (define-public texlive-latex-filecontents
-  (package
-    (name "texlive-latex-filecontents")
-    (version (number->string %texlive-revision))
-    (source (origin
-              (method svn-fetch)
-              (uri (texlive-ref "latex" "filecontents"))
-              (file-name (string-append name "-" version "-checkout"))
-              (sha256
-               (base32
-                "1cmfigg5jx3hmdyh4gv8kwxi7dg076ldkxmr46s05xvhzjig1z9x"))))
-    (build-system texlive-build-system)
-    (arguments '(#:tex-directory "latex/filecontents"))
-    (home-page "https://www.ctan.org/pkg/filecontents")
-    (synopsis "Extended filecontents and filecontents* environments")
-    (description
-     "LaTeX2e's @code{filecontents} and @code{filecontents*} environments
+  (let ((template (simple-texlive-package
+                   "texlive-latex-filecontents"
+                   (list "doc/latex/filecontents/"
+                         "source/latex/filecontents/"
+                         "tex/latex/filecontents/")
+                   (base32
+                    "0ifhqfdzx91hrmndhg5441rpmv9k4lxrql02kd5yx75xpplxryzw"))))
+    (package
+      (inherit template)
+      (arguments
+       (substitute-keyword-arguments (package-arguments template)
+         ((#:tex-directory _ '()) "latex/filecontents")
+         ((#:phases phases)
+          #~(modify-phases #$phases
+              (add-after 'unpack 'chdir
+                (lambda _
+                  (chdir "source/latex/filecontents")))))))
+      (home-page "https://ctan.org/pkg/filecontents")
+      (synopsis "Create an external file from within a LaTeX document")
+      (description
+       "LaTeX2e's @code{filecontents} and @code{filecontents*} environments
 enable a LaTeX source file to generate external files as it runs through
 LaTeX.  However, there are two limitations of these environments: they refuse
-to overwrite existing files, and they can only be used in the preamble of a
-document.  The filecontents package removes these limitations, letting you
-overwrite existing files and letting you use @code{filecontents} /
+to overwrite existing files, and they can only be used in the preamble of
+a document.  The filecontents package removes these limitations, letting you
+overwrite existing files and letting you use @code{filecontents}
 @code{filecontents*} anywhere.")
-    (license license:lppl1.3c+)))
+      (license license:lppl1.3c+))))
 
 (define-public texlive-epsf
   (package