Doc issue Elixir 0.12.2

gistfile1.txt

mix new doctest
cd doctest

Add the following to mix.exs
{ :ex_doc, github: "elixir-lang/ex_doc", ref: "f9c1d88acf8211f41c786750d47e9459b885241f" }

mix deps.get
* Getting ex_doc (git://github.com/elixir-lang/ex_doc.git)
Cloning into '/Users/jimfreeze/Documents/Projects/PlugnPay/doctest/deps/ex_doc'...
remote: Reusing existing pack: 2286, done.
remote: Counting objects: 25, done.
remote: Compressing objects: 100% (22/22), done.
remote: Total 2311 (delta 4), reused 2 (delta 0)
Receiving objects: 100% (2311/2311), 610.75 KiB | 844.00 KiB/s, done.
Resolving deltas: 100% (923/923), done.
Checking connectivity... done
* Compiling ex_doc
git submodule update --init
Submodule 'sundown' (git://github.com/josevalim/sundown.git) registered for path 'sundown'
Cloning into 'sundown'...
Checking connectivity... done
Submodule path 'sundown': checked out '49c3b1323134e973815fb283163ef39b7bda4c6a'
cd sundown && make
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o src/markdown.o src/markdown.c
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o src/stack.o src/stack.c
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o src/buffer.o src/buffer.c
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o src/autolink.o src/autolink.c
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o html/html.o html/html.c
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o html/html_smartypants.o html/html_smartypants.c
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o html/houdini_html_e.o html/houdini_html_e.c
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o html/houdini_href_e.o html/houdini_href_e.c
gcc -g -O3 -Wall -Werror  -shared src/markdown.o src/stack.o src/buffer.o src/autolink.o html/html.o html/html_smartypants.o html/houdini_html_e.o html/houdini_href_e.o -o libsundown.so.1
ln -f -s libsundown.so.1 libsundown.so
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o examples/sundown.o examples/sundown.c
gcc -g -O3 -Wall -Werror  examples/sundown.o src/markdown.o src/stack.o src/buffer.o src/autolink.o html/html.o html/html_smartypants.o html/houdini_html_e.o html/houdini_href_e.o -o sundown
gcc -c -g -O3 -fPIC -Wall -Werror -Wsign-compare -Isrc -Ihtml   -c -o examples/smartypants.o examples/smartypants.c
gcc -g -O3 -Wall -Werror  examples/smartypants.o src/markdown.o src/stack.o src/buffer.o src/autolink.o html/html.o html/html_smartypants.o html/houdini_html_e.o html/houdini_href_e.o -o smartypants
gcc -g -O3 -fPIC -Isundown/src -Isundown/html -I/usr/local/Cellar/erlang-r16/R16B01/lib/erlang/erts-5.10.2/include -shared -dynamiclib -undefined dynamic_lookup -o priv/markdown.so sundown/html/html.o sundown/html/html_smartypants.o sundown/html/houdini_html_e.o sundown/html/houdini_href_e.o sundown/src/buffer.o sundown/src/autolink.o sundown/src/stack.o sundown/src/markdown.o src/markdown_nif.c
Compiled lib/markdown.ex
lib/ex_doc/cli.ex:11: variable project is unused
lib/ex_doc/cli.ex:11: variable source_beam is unused
lib/ex_doc/cli.ex:11: variable version is unused
== Compilation error on file lib/ex_doc/cli.ex ==
could not compile dependency ex_doc, mix compile failed. You can recompile this dependency with `mix deps.compile ex_doc` or update it with `mix deps.update ex_doc`
** (CompileError) lib/ex_doc/cli.ex:24: function source_beam/0 undefined
    (stdlib) lists.erl:1323: :lists.foreach/2
    (stdlib) erl_eval.erl:569: :erl_eval.do_apply/6
    (elixir) src/elixir.erl:140: :elixir.eval_forms/4
    (elixir) src/elixir_lexical.erl:17: :elixir_lexical.run/2


mix deps.compile ex_doc
* Compiling ex_doc
make: `priv/markdown.so' is up to date.
Compiled lib/markdown.ex
lib/ex_doc/cli.ex:11: variable project is unused
lib/ex_doc/cli.ex:11: variable source_beam is unused
lib/ex_doc/cli.ex:11: variable version is unused
== Compilation error on file lib/ex_doc/cli.ex ==
could not compile dependency ex_doc, mix compile failed. You can recompile this dependency with `mix deps.compile ex_doc` or update it with `mix deps.update ex_doc`
** (CompileError) lib/ex_doc/cli.ex:24: function source_beam/0 undefined
    (stdlib) lists.erl:1323: :lists.foreach/2
    (stdlib) erl_eval.erl:569: :erl_eval.do_apply/6
    (elixir) src/elixir.erl:140: :elixir.eval_forms/4
    (elixir) src/elixir_lexical.erl:17: :elixir_lexical.run/2