Trouble packaging a ruby dependency

[Holger Peters <holger.peters@posteo.de>]

I have problems building `ruby-rugged'. The patch below is as far as I 
get,
however it fails with an error message I cannot quite debug. Maybe part 
of the
problem is that `ruby-rugged' bundls libgit and I try to have it use the
system-provided on.

   
`/gnu/store/knrzg013b4bi45bimv315y8r70l99aix-ruby-rugged-1.1.0/lib/ruby/vendor_ruby/extensions/x86_64-linux/2.6.0/rugged-1.1.0/gem_make.out' 
-> 
`/tmp/guix-build-ruby-rugged-1.1.0.drv-0/gem/out/lib/ruby/vendor_ruby/extensions/x86_64-linux/2.6.0/rugged-1.1.0/gem_make.out'
   Backtrace:
              7 (primitive-load 
"/gnu/store/sgdrqfiqfx2dmnqi4qjr8dv4xjf…")
   In ice-9/eval.scm:
      191:35  6 (_ _)
   In guix/build/gnu-build-system.scm:
       838:2  5 (gnu-build #:source _ #:outputs _ #:inputs _ #:phases . 
#)
   In ice-9/boot-9.scm:
     1736:10  4 (with-exception-handler _ _ #:unwind? _ # _)
   In srfi/srfi-1.scm:
      857:16  3 (every1 #<procedure 7ffff4f427a0 at guix/build/gnu-bui…> 
…)
   In guix/build/gnu-build-system.scm:
      847:30  2 (_ _)
   In guix/build/ruby-build-system.scm:
      160:10  1 (install #:inputs _ #:outputs _ #:gem-flags _)
   In ice-9/boot-9.scm:
     1669:16  0 (raise-exception _ #:continuable? _)

This is my definition of ruby-rugged

diff --git a/gnu/packages/ruby.scm b/gnu/packages/ruby.scm
index 2753403834..5754374a3f 100644
--- a/gnu/packages/ruby.scm
+++ b/gnu/packages/ruby.scm
@@ -11715,3 +11715,56 @@ which snapshots to consider and what files to 
include.")
  defined in @file{.travis.yml} on your local machine, using @code{rvm},
  @code{rbenv}, or @code{chruby} to test different versions of Ruby.")
      (license license:expat)))
+
+(define-public ruby-rugged
+  (package
+    (name "ruby-rugged")
+    (version "1.1.0")
+    (home-page "https://www.rubydoc.info/gems/rugged")
+    (source
+     (origin
+       (method url-fetch)
+       (uri (rubygems-uri "rugged" version))
+       (sha256
+        (base32 
"04aq913plcxjw71l5r62qgz3bx3466p0wvgyfqahg5n3nybmcwqy"))))
+    (build-system ruby-build-system)
+    (arguments
+     `(#:tests? #f
+       #:gem-flags (list  "--" "--use-system-libraries")))
+    (inputs
+     `(("libgit2" ,libgit2)))
+    (native-inputs
+     `(("ruby-minitest" ,ruby-minitest)
+       ("ruby-pry" ,ruby-pry)
+       ("ruby-rake-compiler" ,ruby-rake-compiler)))
+    (synopsis "Ruby bindings to the libgit2 linkable C Git library.  ")
+    (description "Rugged is a library for accessing libgit2 in Ruby. It 
gives
+you the speed and portability of libgit2 with the beauty of the Ruby
+language.")
+    (license license:expat)))