Merge remote-tracking branch 'canonical/next'

* canonical/next:
  fix nasty bug that didn't let relcool output errors
  make the default output _rel instead of relcool_output
  allow a user to specify additional opts to erlexec
  add examples of simple and complete relcool configs
  make sure ebin is removed on clean
  add inadvertantly deleted relcool.app.src
  support travis CI in relcool
  cleanup the rebar config
  remove docs (they have been moved to the wiki)
  all relcool to symlink in 'overridden' apps
  rcl_prv_discover now supports setting up 'link' type app_info messages
  support specifing overrides in the configuration
  support a new 'link' field in rcl_app_info
  minor cleanup and refactoring for rcl_prv_assembler, rcl_prv_discover

20 files changed, 311 insertions, 668 deletions

diff --git a/.gitignore b/.gitignore
index 4e58778..bf72009 100644
--- a/.gitignore
+++ b/.gitignore
@@ -8,5 +8,5 @@ relcool
 src/rcl_goal.erl
 logs
 test/*_data
-relcool_output/*
+_rel/*
 .*
\ No newline at end of file
diff --git a/.travis.yml b/.travis.yml
new file mode 100644
index 0000000..3832235
--- /dev/null
+++ b/.travis.yml
@@ -0,0 +1,13 @@
+language: erlang
+otp_release:
+  - R15B02
+  - R15B01
+  - R15B
+  - R14B04
+  - R14B03
+  - R14B02
+script: "make rebuild"
+branches:
+  only:
+    - master
+    - next
\ No newline at end of file
diff --git a/Makefile b/Makefile
index 599bcb3..2e43f9d 100644
--- a/Makefile
+++ b/Makefile
@@ -41,15 +41,6 @@ endif
 all: compile escript dialyzer test
 
 # =============================================================================
-# Include relevant sub-makefiles.
-# =============================================================================
-# These are not subdirs, they are just additional makefile information
-# that happens to live subdirectories
-
-include $(CURDIR)/docs/docs.mkf
-
-
-# =============================================================================
 # Rules to build the system
 # =============================================================================
 
@@ -107,6 +98,7 @@ clean-common-test-data:
 clean: clean-common-test-data
 	- rm -rf $(CURDIR)/test/*.beam
 	- rm -rf $(CURDIR)/logs
+	- rm -rf $(CURDIR)/ebin
 	$(REBAR) skip_deps=true clean
 
 distclean: clean
diff --git a/docs/conf.py b/docs/conf.py
deleted file mode 100644
index f29af4c..0000000
--- a/docs/conf.py
+++ /dev/null
@@ -1,285 +0,0 @@
-# -*- coding: utf-8 -*-
-#
-# Relcool documentation build configuration file, created by
-# sphinx-quickstart on Mon Sep 10 10:04:06 2012.
-#
-# This file is execfile()d with the current directory set to its containing dir.
-#
-# Note that not all possible configuration values are present in this
-# autogenerated file.
-#
-# All configuration values have a default; values that are commented out
-# serve to show the default.
-
-import sys, os
-
-# If extensions (or modules to document with autodoc) are in another directory,
-# add these directories to sys.path here. If the directory is relative to the
-# documentation root, use os.path.abspath to make it absolute, like shown here.
-#sys.path.insert(0, os.path.abspath('.'))
-
-# -- General configuration -----------------------------------------------------
-
-# If your documentation needs a minimal Sphinx version, state it here.
-#needs_sphinx = '1.0'
-
-# Add any Sphinx extension module names here, as strings. They can be extensions
-# coming with Sphinx (named 'sphinx.ext.*') or your custom ones.
-extensions = []
-
-# Add any paths that contain templates here, relative to this directory.
-templates_path = ['_templates']
-
-# The suffix of source filenames.
-source_suffix = '.rst'
-
-# The encoding of source files.
-#source_encoding = 'utf-8-sig'
-
-# The master toctree document.
-master_doc = 'index'
-
-# General information about the project.
-project = u'Relcool'
-copyright = u'2012, Eric B MErritt'
-
-# The version info for the project you're documenting, acts as replacement for
-# |version| and |release|, also used in various other places throughout the
-# built documents.
-#
-# The short X.Y version.
-version = '0.0.1'
-# The full version, including alpha/beta/rc tags.
-release = '0.0.1'
-
-# The language for content autogenerated by Sphinx. Refer to documentation
-# for a list of supported languages.
-#language = None
-
-# There are two options for replacing |today|: either, you set today to some
-# non-false value, then it is used:
-#today = ''
-# Else, today_fmt is used as the format for a strftime call.
-#today_fmt = '%B %d, %Y'
-
-# List of patterns, relative to source directory, that match files and
-# directories to ignore when looking for source files.
-exclude_patterns = ['_build']
-
-# The reST default role (used for this markup: `text`) to use for all documents.
-#default_role = None
-
-# If true, '()' will be appended to :func: etc. cross-reference text.
-#add_function_parentheses = True
-
-# If true, the current module name will be prepended to all description
-# unit titles (such as .. function::).
-#add_module_names = True
-
-# If true, sectionauthor and moduleauthor directives will be shown in the
-# output. They are ignored by default.
-#show_authors = False
-
-# The name of the Pygments (syntax highlighting) style to use.
-pygments_style = 'sphinx'
-
-# A list of ignored prefixes for module index sorting.
-#modindex_common_prefix = []
-
-
-# -- Options for HTML output ---------------------------------------------------
-
-# The theme to use for HTML and HTML Help pages.  See the documentation for
-# a list of builtin themes.
-html_theme = 'default'
-
-# Theme options are theme-specific and customize the look and feel of a theme
-# further.  For a list of options available for each theme, see the
-# documentation.
-#html_theme_options = {}
-
-# Add any paths that contain custom themes here, relative to this directory.
-#html_theme_path = []
-
-# The name for this set of Sphinx documents.  If None, it defaults to
-# "<project> v<release> documentation".
-#html_title = None
-
-# A shorter title for the navigation bar.  Default is the same as html_title.
-#html_short_title = None
-
-# The name of an image file (relative to this directory) to place at the top
-# of the sidebar.
-#html_logo = None
-
-# The name of an image file (within the static path) to use as favicon of the
-# docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
-# pixels large.
-#html_favicon = None
-
-# Add any paths that contain custom static files (such as style sheets) here,
-# relative to this directory. They are copied after the builtin static files,
-# so a file named "default.css" will overwrite the builtin "default.css".
-html_static_path = ['_static']
-
-# If not '', a 'Last updated on:' timestamp is inserted at every page bottom,
-# using the given strftime format.
-#html_last_updated_fmt = '%b %d, %Y'
-
-# If true, SmartyPants will be used to convert quotes and dashes to
-# typographically correct entities.
-#html_use_smartypants = True
-
-# Custom sidebar templates, maps document names to template names.
-#html_sidebars = {}
-
-# Additional templates that should be rendered to pages, maps page names to
-# template names.
-#html_additional_pages = {}
-
-# If false, no module index is generated.
-#html_domain_indices = True
-
-# If false, no index is generated.
-#html_use_index = True
-
-# If true, the index is split into individual pages for each letter.
-#html_split_index = False
-
-# If true, links to the reST sources are added to the pages.
-#html_show_sourcelink = True
-
-# If true, "Created using Sphinx" is shown in the HTML footer. Default is True.
-#html_show_sphinx = True
-
-# If true, "(C) Copyright ..." is shown in the HTML footer. Default is True.
-#html_show_copyright = True
-
-# If true, an OpenSearch description file will be output, and all pages will
-# contain a <link> tag referring to it.  The value of this option must be the
-# base URL from which the finished HTML is served.
-#html_use_opensearch = ''
-
-# This is the file name suffix for HTML files (e.g. ".xhtml").
-#html_file_suffix = None
-
-# Output file base name for HTML help builder.
-htmlhelp_basename = 'Relcooldoc'
-
-
-# -- Options for LaTeX output --------------------------------------------------
-
-latex_elements = {
-# The paper size ('letterpaper' or 'a4paper').
-#'papersize': 'letterpaper',
-
-# The font size ('10pt', '11pt' or '12pt').
-#'pointsize': '10pt',
-
-# Additional stuff for the LaTeX preamble.
-#'preamble': '',
-}
-
-# Grouping the document tree into LaTeX files. List of tuples
-# (source start file, target name, title, author, documentclass [howto/manual]).
-latex_documents = [
-  ('index', 'Relcool.tex', u'Relcool Documentation',
-   u'Eric B MErritt', 'manual'),
-]
-
-# The name of an image file (relative to this directory) to place at the top of
-# the title page.
-#latex_logo = None
-
-# For "manual" documents, if this is true, then toplevel headings are parts,
-# not chapters.
-#latex_use_parts = False
-
-# If true, show page references after internal links.
-#latex_show_pagerefs = False
-
-# If true, show URL addresses after external links.
-#latex_show_urls = False
-
-# Documents to append as an appendix to all manuals.
-#latex_appendices = []
-
-# If false, no module index is generated.
-#latex_domain_indices = True
-
-
-# -- Options for manual page output --------------------------------------------
-
-# One entry per manual page. List of tuples
-# (source start file, name, description, authors, manual section).
-man_pages = [
-    ('index', 'relcool', u'Relcool Documentation',
-     [u'Eric B MErritt'], 1)
-]
-
-# If true, show URL addresses after external links.
-#man_show_urls = False
-
-
-# -- Options for Texinfo output ------------------------------------------------
-
-# Grouping the document tree into Texinfo files. List of tuples
-# (source start file, target name, title, author,
-#  dir menu entry, description, category)
-texinfo_documents = [
-  ('index', 'Relcool', u'Relcool Documentation',
-   u'Eric B MErritt', 'Relcool', 'One line description of project.',
-   'Miscellaneous'),
-]
-
-# Documents to append as an appendix to all manuals.
-#texinfo_appendices = []
-
-# If false, no module index is generated.
-#texinfo_domain_indices = True
-
-# How to display URL addresses: 'footnote', 'no', or 'inline'.
-#texinfo_show_urls = 'footnote'
-
-
-# -- Options for Epub output ---------------------------------------------------
-
-# Bibliographic Dublin Core info.
-epub_title = u'Relcool'
-epub_author = u'Eric B MErritt'
-epub_publisher = u'Eric B MErritt'
-epub_copyright = u'2012, Eric B MErritt'
-
-# The language of the text. It defaults to the language option
-# or en if the language is not set.
-#epub_language = ''
-
-# The scheme of the identifier. Typical schemes are ISBN or URL.
-#epub_scheme = ''
-
-# The unique identifier of the text. This can be a ISBN number
-# or the project homepage.
-#epub_identifier = ''
-
-# A unique identification for the text.
-#epub_uid = ''
-
-# A tuple containing the cover image and cover page html template filenames.
-#epub_cover = ()
-
-# HTML files that should be inserted before the pages created by sphinx.
-# The format is a list of tuples containing the path and title.
-#epub_pre_files = []
-
-# HTML files shat should be inserted after the pages created by sphinx.
-# The format is a list of tuples containing the path and title.
-#epub_post_files = []
-
-# A list of files that should not be packed into the epub file.
-#epub_exclude_files = []
-
-# The depth of the table of contents in toc.ncx.
-#epub_tocdepth = 3
-
-# Allow duplicate toc entries.
-#epub_tocdup = True
diff --git a/docs/configuration.rst b/docs/configuration.rst
deleted file mode 100644
index 4e84deb..0000000
--- a/docs/configuration.rst
+++ /dev/null
@@ -1,89 +0,0 @@
-Configuration
-=============
-
-Configuration of reltool is done via Erlang key, value elements in the
-`relcool.config` file. There are various configuration elements that
-can appear, each affects the running of the system in specific
-ways. Note that these must be complete Erlang terms terminated by a
-`.`.
-
-Paths
------
-
-Paths is a way to add additional code paths (that point to Erlang beam
-files) to the system. These are not used for dependency resolution,
-they are only used as code paths. The main use for this is simply to
-provide a non-resolvable path for additional providers.
-
-the path confuration element looks as follows::
-
-    {paths, [<list of directory paths>]}.
-
-So if we wanted to add `/usr/local/lib` and `/opt/lib` to the code
-paths for the system we could add the following::
-
-    {paths, ["/usr/local/lib", "/opt/lib"]}.
-
-to our configuration.
-
-Providers
----------
-
-Providers are how the Relcool system can be extended by a user. They
-are basically Erlang modules that implement the `rcl_provider`
-behaviour and are available via a code path. See the section on
-providers for more information.
-
-The `providers` element provides a completely new list of providers,
-replacing any providers that may already exist. The provider element
-is as follows::
-
-     {providers, <list of module names>}.
-
-Lets say I have three providers; `my_custom_assembler`,
-`my_rpm_assembler` and `my_deb_assembler`. I could make these the
-complete list of providers by doing the following in my config::
-
-    {providers, [my_custom_assembler,
-                 my_rpm_assembler,
-                 my_deb_assembler]}.
-
-Order is important in the providers as they will be executed in the
-order specified.
-
-Add Providers
--------------
-
-`add_providers` is very similar to `providers` with the exception that
-the listed providers are added to the end of the current list of
-providers rather then replacing the list all together. Add providres
-looks as follows::
-
-
-     {add_providers, <list of module names>}.
-
-Lets take our previous example but only add `my_rpm_assembler` and
-`my_deb_assembler` to the existing list of providers. We do this by
-adding the following::
-
-    {add_providers, [my_rpm_assembler,
-                     my_deb_assembler]}.
-
-Releases
---------
-
-Release configuration is the bread and butter, the blood and bones of
-the Relcool system. It provides the framework for realizing
-dependencies in the system. The release element basically minics the
-standard _Erlang/OTP Release Metadata file format:
-http://www.erlang.org/doc/man/rel.html. There are two main
-differences. The first is that you don't have to specify a complete
-list of applications and you may specify version constraints instead
-of hard versions.
-
-
-{release, {relname, vsn},
-  app goals}
-{release, {relname, vsn},
-{erts, vsn},
-app goals}
diff --git a/docs/docs.mkf b/docs/docs.mkf
deleted file mode 100644
index 6987063..0000000
--- a/docs/docs.mkf
+++ /dev/null
@@ -1,154 +0,0 @@
-# -*- mode: Makefile; fill-column: 80; comment-column: 75; -*-
-# Makefile for Sphinx documentation
-#
-
-# You can set these variables from the command line.
-SPHINXOPTS    =
-SPHINXBUILD   = sphinx-build
-PAPER         =
-BUILDDIR      = _build
-
-# Internal variables.
-PAPEROPT_a4     = -D latex_paper_size=a4
-PAPEROPT_letter = -D latex_paper_size=letter
-ALLSPHINXOPTS   = -d $(BUILDDIR)/doctrees $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
-# the i18n builder cannot share the environment and doctrees with the others
-I18NSPHINXOPTS  = $(PAPEROPT_$(PAPER)) $(SPHINXOPTS) .
-
-.PHONY: help clean html dirhtml singlehtml pickle json htmlhelp qthelp devhelp epub latex latexpdf text man changes linkcheck doctest gettext
-
-doc-help:
-	@echo "Please use \`make <target>' where <target> is one of"
-	@echo "  html       to make standalone HTML files"
-	@echo "  dirhtml    to make HTML files named index.html in directories"
-	@echo "  singlehtml to make a single large HTML file"
-	@echo "  pickle     to make pickle files"
-	@echo "  json       to make JSON files"
-	@echo "  htmlhelp   to make HTML files and a HTML help project"
-	@echo "  qthelp     to make HTML files and a qthelp project"
-	@echo "  devhelp    to make HTML files and a Devhelp project"
-	@echo "  epub       to make an epub"
-	@echo "  latex      to make LaTeX files, you can set PAPER=a4 or PAPER=letter"
-	@echo "  latexpdf   to make LaTeX files and run them through pdflatex"
-	@echo "  text       to make text files"
-	@echo "  man        to make manual pages"
-	@echo "  texinfo    to make Texinfo files"
-	@echo "  info       to make Texinfo files and run them through makeinfo"
-	@echo "  gettext    to make PO message catalogs"
-	@echo "  changes    to make an overview of all changed/added/deprecated items"
-	@echo "  linkcheck  to check all external links for integrity"
-	@echo "  doctest    to run all doctests embedded in the documentation (if enabled)"
-
-doc-clean:
-	-rm -rf $(BUILDDIR)/*
-
-html:
-	$(SPHINXBUILD) -b html $(ALLSPHINXOPTS) $(BUILDDIR)/html
-	@echo
-	@echo "Build finished. The HTML pages are in $(BUILDDIR)/html."
-
-dirhtml:
-	$(SPHINXBUILD) -b dirhtml $(ALLSPHINXOPTS) $(BUILDDIR)/dirhtml
-	@echo
-	@echo "Build finished. The HTML pages are in $(BUILDDIR)/dirhtml."
-
-singlehtml:
-	$(SPHINXBUILD) -b singlehtml $(ALLSPHINXOPTS) $(BUILDDIR)/singlehtml
-	@echo
-	@echo "Build finished. The HTML page is in $(BUILDDIR)/singlehtml."
-
-pickle:
-	$(SPHINXBUILD) -b pickle $(ALLSPHINXOPTS) $(BUILDDIR)/pickle
-	@echo
-	@echo "Build finished; now you can process the pickle files."
-
-json:
-	$(SPHINXBUILD) -b json $(ALLSPHINXOPTS) $(BUILDDIR)/json
-	@echo
-	@echo "Build finished; now you can process the JSON files."
-
-htmlhelp:
-	$(SPHINXBUILD) -b htmlhelp $(ALLSPHINXOPTS) $(BUILDDIR)/htmlhelp
-	@echo
-	@echo "Build finished; now you can run HTML Help Workshop with the" \
-	      ".hhp project file in $(BUILDDIR)/htmlhelp."
-
-qthelp:
-	$(SPHINXBUILD) -b qthelp $(ALLSPHINXOPTS) $(BUILDDIR)/qthelp
-	@echo
-	@echo "Build finished; now you can run "qcollectiongenerator" with the" \
-	      ".qhcp project file in $(BUILDDIR)/qthelp, like this:"
-	@echo "# qcollectiongenerator $(BUILDDIR)/qthelp/Relcool.qhcp"
-	@echo "To view the help file:"
-	@echo "# assistant -collectionFile $(BUILDDIR)/qthelp/Relcool.qhc"
-
-devhelp:
-	$(SPHINXBUILD) -b devhelp $(ALLSPHINXOPTS) $(BUILDDIR)/devhelp
-	@echo
-	@echo "Build finished."
-	@echo "To view the help file:"
-	@echo "# mkdir -p $$HOME/.local/share/devhelp/Relcool"
-	@echo "# ln -s $(BUILDDIR)/devhelp $$HOME/.local/share/devhelp/Relcool"
-	@echo "# devhelp"
-
-epub:
-	$(SPHINXBUILD) -b epub $(ALLSPHINXOPTS) $(BUILDDIR)/epub
-	@echo
-	@echo "Build finished. The epub file is in $(BUILDDIR)/epub."
-
-latex:
-	$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
-	@echo
-	@echo "Build finished; the LaTeX files are in $(BUILDDIR)/latex."
-	@echo "Run \`make' in that directory to run these through (pdf)latex" \
-	      "(use \`make latexpdf' here to do that automatically)."
-
-latexpdf:
-	$(SPHINXBUILD) -b latex $(ALLSPHINXOPTS) $(BUILDDIR)/latex
-	@echo "Running LaTeX files through pdflatex..."
-	$(MAKE) -C $(BUILDDIR)/latex all-pdf
-	@echo "pdflatex finished; the PDF files are in $(BUILDDIR)/latex."
-
-text:
-	$(SPHINXBUILD) -b text $(ALLSPHINXOPTS) $(BUILDDIR)/text
-	@echo
-	@echo "Build finished. The text files are in $(BUILDDIR)/text."
-
-man:
-	$(SPHINXBUILD) -b man $(ALLSPHINXOPTS) $(BUILDDIR)/man
-	@echo
-	@echo "Build finished. The manual pages are in $(BUILDDIR)/man."
-
-texinfo:
-	$(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/texinfo
-	@echo
-	@echo "Build finished. The Texinfo files are in $(BUILDDIR)/texinfo."
-	@echo "Run \`make' in that directory to run these through makeinfo" \
-	      "(use \`make info' here to do that automatically)."
-
-info:
-	$(SPHINXBUILD) -b texinfo $(ALLSPHINXOPTS) $(BUILDDIR)/texinfo
-	@echo "Running Texinfo files through makeinfo..."
-	make -C $(BUILDDIR)/texinfo info
-	@echo "makeinfo finished; the Info files are in $(BUILDDIR)/texinfo."
-
-gettext:
-	$(SPHINXBUILD) -b gettext $(I18NSPHINXOPTS) $(BUILDDIR)/locale
-	@echo
-	@echo "Build finished. The message catalogs are in $(BUILDDIR)/locale."
-
-changes:
-	$(SPHINXBUILD) -b changes $(ALLSPHINXOPTS) $(BUILDDIR)/changes
-	@echo
-	@echo "The overview file is in $(BUILDDIR)/changes."
-
-linkcheck:
-	$(SPHINXBUILD) -b linkcheck $(ALLSPHINXOPTS) $(BUILDDIR)/linkcheck
-	@echo
-	@echo "Link check complete; look for any errors in the above output " \
-	      "or in $(BUILDDIR)/linkcheck/output.txt."
-
-doctest:
-	$(SPHINXBUILD) -b doctest $(ALLSPHINXOPTS) $(BUILDDIR)/doctest
-	@echo "Testing of doctests in the sources finished, look at the " \
-	      "results in $(BUILDDIR)/doctest/output.txt."
diff --git a/docs/index.rst b/docs/index.rst
deleted file mode 100644
index f367ef8..0000000
--- a/docs/index.rst
+++ /dev/null
@@ -1,22 +0,0 @@
-.. Relcool documentation master file, created by
-   sphinx-quickstart on Mon Sep 10 10:04:06 2012.
-   You can adapt this file completely to your liking, but it should at least
-   contain the root `toctree` directive.
-
-Welcome to Relcool's documentation!
-===================================
-
-Contents:
-
-.. toctree::
-   :maxdepth: 2
-
-
-
-Indices and tables
-==================
-
-* :ref:`genindex`
-* :ref:`modindex`
-* :ref:`search`
-
diff --git a/docs/overview.rst b/docs/overview.rst
deleted file mode 100644
index 77453a3..0000000
--- a/docs/overview.rst
+++ /dev/null
@@ -1,58 +0,0 @@
-Overview
-========
-
-Relcool is a tool that, given a specification, assembles
-releases. That is it makes an assessment of all of the Erlang/OTP Apps
-available to it and the constraints that you supply as part of your
-configuration and resolves a complete set of OTP Applications and
-thier versions for use in the release. This may be a bit hard to
-understand if you are not familiar with the way version resolutions
-work in package management systems. So lets look at an example.
-
-Lets say that you have the following OTP Applications
-
-* app1-1.2
-   with dependencies::
-     app2
-     app5
-     app6
-* app1-1.3
-   with dependencies::
-     app2
-     app6
-* app2-2.0
-  with dependencies::
-    app6
-* app2-2.1
-    with dependencies::
-    app6
-    app7
-* app3-2.0
-* app4-1.0.0
-* app5-3.0
-* app6-1.0
-  with dependencies::
-   app3
-* app7-2.0
-
-This is the world of OTP Apps your Relcool knows about (basically OTP
-Apps in the Library Directories you have specified). You have set a
-config that looks like the following::
-
-    {release, {awesome_supercool, "1.0"},
-        [{app1, "1.3", '>='},
-         {app2, "2.0", '>'},
-         app3]}
-
-When the Relcool process has run you will end up with a complete release as follows::
-
-    {release, {awesome_supercool, "1.0"},
-      [{app1, "1.3"},
-       {app2, "2.1"},
-       {app3, "2.0"},
-       {app6, "1.0"},
-       {app7, "2.0"}]}
-
-As you can see that is a fully realied view of your direct and
-transative dependencies based on the world that Relcool knows about
-and the constraints that you specified in your configuration.
diff --git a/examples/relcool.config b/examples/relcool.config
new file mode 100644
index 0000000..fe6182b
--- /dev/null
+++ b/examples/relcool.config
@@ -0,0 +1,74 @@
+%% -*- mode: Erlang; fill-column: 80; comment-column: 75; -*-
+%% Example Relcool Config
+%% ======================
+%%
+%% This is an example relcool config whose purpose is to demonstrate all of the
+%% options available in relcool. Its not expected that you will use all of the
+%% things here. In fact, there is a high likely hood that *your* relcool.config
+%% will be extremely minimal, as relcool does a very good job of figuring out
+%% things on its own.
+%%
+%% The Release We Are Building
+%% ---------------------------
+%%
+%% Lets say we have a release called sexpr. The sexpr release supports versions
+%% 0.0.1 and 0.0.2 with different dependencies. 0.0.1 requires erlware commons
+%% 0.8.0 or lesser. 0.0.2 requires erlware_commons 0.8.1 or greater along with
+%% neotoma (any version). We also do not want neotoma to be loaded. We also want
+%% our default release. the one we build in the common case to be sexper 0.0.2.
+
+%% You can tell relcool about additional directories that you want searched for
+%% otp apps during the discovery process. You do that in the 'paths' config. You
+%% can also specify these paths on the command line with `-p`. Be aware that
+%% relcool plays well with rebar so if you have a deps directory in the current
+%% directory it will be automatically added.
+{paths, ["/opt/erlang_apps"]}.
+
+
+%% If you have a sys.config file you need to tell relcool where it is. If you do
+%% that relcool will include the sys.config in the appropriate place
+%% automatically.
+{sys_config, "./config/sys.config"}.
+
+%% relcool will include erts by default. However, if you don't want to include
+%% erts you can add the `include_erts` tuple to the config and tell relcool not
+%% to include it.
+{include_erts, false}.
+
+%% When we have multiple releases relcool needs to know which one to build. You
+%% can specify that on the command line with the `-n` and `-v` arguments to
+%% relcool. However, it is often more convenient to do it in the config.
+{default_release, sexpr, "0.0.2"}.
+
+{release, {sexpr, "0.0.1"},
+ [sexpr,
+  %% There are two syntaxes for constraints.
+  %% The first is the tuple syntax shown here.
+  {erlware_commons, "0.8.0", '<='}]}.
+
+{release, {sexpr, "0.0.2"},
+ [sexpr,
+
+  %% This is the second constraint syntax, it is interchangeable with the tuple
+  %% syntax and its up to you which you find more readable/usable.
+  "erlware_commons>=0.8.1",
+
+  %% You can put the release load types in the release spec here in exactly the
+  %% same way that you can do it for a normal relfile. The syntax is
+  %% {<constraint>, <type>}.
+  {neotoma, load}]}.
+
+%% During development its often the case that you want to substitute the app
+%% that you are working on for a 'production' version of an app. You can
+%% explicitly tell relcool to override all versions of an app that you specify
+%% with an app in an arbitrary directory. Relcool will then symlink that app
+%% into the release in place of the specified app. be aware though that relcool
+%% will check your app for consistancy so it should be a normal OTP app and
+%% already be built.
+{overrides, [{sexpr, "../sexpr"}]}.
+
+
+%% In some cases you might want to add additional functionality to relcool. You
+%% can do this via a 'provider'. A provider is an implementation of the relcool
+%% provider behaviour. This probably shouldn't be needed very often.
+{add_providers, [my_custom_functionality]}.
diff --git a/examples/relcool_simple.config b/examples/relcool_simple.config
new file mode 100644
index 0000000..88e9e8d
--- /dev/null
+++ b/examples/relcool_simple.config
@@ -0,0 +1,19 @@
+%% -*- mode: Erlang; fill-column: 80; comment-column: 75; -*-
+%% Example Relcool Simple Config
+%% =============================
+%%
+%% This is an example relcool config whose purpose demonstrate the minimal
+%% config needed for relcool. For a more complete example see the relcool.config
+%% in the examples directory.
+%%
+%% The Release We Are Building
+%% ---------------------------
+%%
+%% Lets say we have a release called sexpr. The sexpr release has version 0.0.2
+%% 0.0.2 requires erlware_commons 0.8.1 or greater along with neotoma
+%% (any version).
+
+{release, {sexpr, "0.0.2"},
+ [sexpr,
+  {erlware_commons, 0.8.1, '>='},
+  neotoma]}.
diff --git a/rebar.config b/rebar.config
index 2211100..2b2f0b3 100644
--- a/rebar.config
+++ b/rebar.config
@@ -1,5 +1,5 @@
 %% -*- mode: Erlang; fill-column: 80; comment-column: 75; -*-
-
+%% Dependencies ================================================================
 {deps, [{rebar_vsn_plugin, ".*",
          {git, "https://github.com/erlware/rebar_vsn_plugin.git",
           {tag, "master"}}},
@@ -12,14 +12,21 @@
          {git, "https://github.com/jcomellas/getopt.git",
           {branch, "master"}}}]}.
 
+%% Rebar Plugins ==============================================================
 {plugins, [rebar_vsn_plugin]}.
 
-{escript_incl_apps,
- [getopt, erlware_commons]}.
-
-{first_files, [rcl_provider]}.
+%% Compiler Options ============================================================
+{erl_opts,
+    [debug_info, warnings_as_errors, inline]}.
 
+%% EUnit =======================================================================
+{eunit_opts,
+    [verbose, {report, {eunit_surefire, [{dir, "."}]}}]}.
 {cover_enabled, true}.
 {cover_print_enabled, true}.
 
-{erl_opts, [debug_info, warnings_as_errors, inline]}.
+%% Misc =======================================================================
+{escript_incl_apps,
+ [getopt, erlware_commons]}.
+
+{first_files, [rcl_provider]}.
diff --git a/src/rcl_app_info.erl b/src/rcl_app_info.erl
index d0192e6..bc64e30 100644
--- a/src/rcl_app_info.erl
+++ b/src/rcl_app_info.erl
@@ -49,6 +49,8 @@
          active_deps/2,
          library_deps/1,
          library_deps/2,
+         link/1,
+         link/2,
          format_error/1,
          format/2,
          format/1]).
@@ -60,6 +62,7 @@
 -record(app_info_t, {name :: atom(),
                      vsn :: ec_semver:semver(),
                      dir :: file:name(),
+                     link=false :: boolean(),
                      active_deps :: [atom()],
                      library_deps :: [atom()]}).
 
@@ -80,7 +83,13 @@ new() ->
 %% @doc build a complete version of the app info with all fields set.
 -spec new(atom(), string(), file:name(), [atom()], [atom()]) ->
                  {ok, t()} | relcool:error().
-new(AppName, Vsn, Dir, ActiveDeps, LibraryDeps)
+new(AppName, Vsn, Dir, ActiveDeps, LibraryDeps) ->
+    new(AppName, Vsn, Dir, ActiveDeps, LibraryDeps, false).
+
+%% @doc build a complete version of the app info with all fields set.
+-spec new(atom(), string(), file:name(), [atom()], [atom()], boolean()) ->
+                 {ok, t()} | relcool:error().
+new(AppName, Vsn, Dir, ActiveDeps, LibraryDeps, Link)
   when erlang:is_atom(AppName),
        erlang:is_list(Dir),
        erlang:is_list(ActiveDeps),
@@ -91,7 +100,8 @@ new(AppName, Vsn, Dir, ActiveDeps, LibraryDeps)
         ParsedVsn ->
             {ok, #app_info_t{name=AppName, vsn=ParsedVsn, dir=Dir,
                              active_deps=ActiveDeps,
-                             library_deps=LibraryDeps}}
+                             library_deps=LibraryDeps,
+                             link=Link}}
     end.
 
 -spec name(t()) -> atom().
@@ -145,6 +155,14 @@ library_deps(AppInfo=#app_info_t{}, LibraryDeps)
   when erlang:is_list(LibraryDeps) ->
     AppInfo#app_info_t{library_deps=LibraryDeps}.
 
+-spec link(t()) -> boolean().
+link(#app_info_t{link=Link}) ->
+    Link.
+
+-spec link(t(), boolean()) -> t().
+link(AppInfo, NewLink) ->
+    AppInfo#app_info_t{link=NewLink}.
+
 -spec format_error(Reason::term()) -> iolist().
 format_error({vsn_parse, AppName}) ->
     io_lib:format("Error parsing version for ~p",
@@ -156,9 +174,11 @@ format(AppInfo) ->
 
 -spec format(non_neg_integer(), t()) -> iolist().
 format(Indent, #app_info_t{name=Name, vsn=Vsn, dir=Dir,
-                           active_deps=Deps, library_deps=LibDeps}) ->
+                           active_deps=Deps, library_deps=LibDeps,
+                           link=Link}) ->
     [rcl_util:indent(Indent), erlang:atom_to_list(Name), "-", ec_semver:format(Vsn),
      ": ", Dir, "\n",
+     rcl_util:indent(Indent + 1), "Symlink: ", erlang:atom_to_list(Link), "\n",
      rcl_util:indent(Indent + 1), "Active Dependencies:\n",
      [[rcl_util:indent(Indent + 2), erlang:atom_to_list(Dep), ",\n"] || Dep <- Deps],
      rcl_util:indent(Indent + 1), "Library Dependencies:\n",
diff --git a/src/rcl_cmd_args.erl b/src/rcl_cmd_args.erl
index ab073a2..68bd9ce 100644
--- a/src/rcl_cmd_args.erl
+++ b/src/rcl_cmd_args.erl
@@ -147,7 +147,7 @@ convert_goals([RawSpec | Rest], Acc) ->
 -spec create_output_dir([getopt:option()], rcl_state:cmd_args()) ->
                                {ok, rcl_state:cmd_args()} | relcool:error().
 create_output_dir(Opts, Acc) ->
-    OutputDir = proplists:get_value(output_dir, Opts, "./relcool_output"),
+    OutputDir = proplists:get_value(output_dir, Opts, "./_rel"),
     case filelib:is_dir(OutputDir) of
         false ->
             case rcl_util:mkdir_p(OutputDir) of
diff --git a/src/rcl_provider.erl b/src/rcl_provider.erl
index 9d1dd88..c3ef434 100644
--- a/src/rcl_provider.erl
+++ b/src/rcl_provider.erl
@@ -10,6 +10,7 @@
 %% API
 -export([new/2,
          do/2,
+         impl/1,
          format_error/1,
          format_error/2,
          format/1]).
@@ -57,6 +58,12 @@ new(ModuleName, State0) when is_atom(ModuleName) ->
 do({?MODULE, Mod}, State) ->
     Mod:do(State).
 
+%%% @doc get the name of the module that implements the provider
+%%% @param Provider the provider object
+-spec impl(Provider::t()) -> module().
+impl({?MODULE, Mod}) ->
+    Mod.
+
 %% @doc format an error produced from a provider.
 -spec format_error(Reason::term()) -> iolist().
 format_error({non_existing, ModuleName}) ->
diff --git a/src/rcl_prv_assembler.erl b/src/rcl_prv_assembler.erl
index a118b12..c0f65c9 100644
--- a/src/rcl_prv_assembler.erl
+++ b/src/rcl_prv_assembler.erl
@@ -73,8 +73,6 @@ format_error({release_script_generation_error, Module, Errors}) ->
     ["Errors generating release \n",
      rcl_util:indent(1), Module:format_error(Errors)].
 
-
-
 %%%===================================================================
 %%% Internal Functions
 %%%===================================================================
@@ -102,15 +100,20 @@ copy_app(LibDir, App) ->
     AppVsn = rcl_app_info:vsn_as_string(App),
     AppDir = rcl_app_info:dir(App),
     TargetDir = filename:join([LibDir, AppName ++ "-" ++ AppVsn]),
-    ec_plists:map(fun(SubDir) ->
-                          copy_dir(AppDir, TargetDir, SubDir)
-                  end, ["ebin",
-                        "include",
-                        "priv",
-                        "src",
-                        "c_src",
-                        "README",
-                        "LICENSE"]).
+    case rcl_app_info:link(App) of
+        true ->
+            file:make_symlink(AppDir, TargetDir);
+        false ->
+            ec_plists:map(fun(SubDir) ->
+                                  copy_dir(AppDir, TargetDir, SubDir)
+                          end, ["ebin",
+                                "include",
+                                "priv",
+                                "src",
+                                "c_src",
+                                "README",
+                                "LICENSE"])
+    end.
 
 copy_dir(AppDir, TargetDir, SubDir) ->
     SubSource = filename:join(AppDir, SubDir),
@@ -157,7 +160,10 @@ write_bin_file(State, Release, OutputDir, RelDir) ->
     ok = ec_file:mkdir_p(BinDir),
     VsnRel = filename:join(BinDir, RelName ++ "-" ++ RelVsn),
     BareRel = filename:join(BinDir, RelName),
-    StartFile = bin_file_contents(RelName, RelVsn, rcl_release:erts(Release)),
+    ErlOpts = rcl_state:get(State, erl_opts, ""),
+    StartFile = bin_file_contents(RelName, RelVsn,
+                                  rcl_release:erts(Release),
+ ErlOpts),
     ok = file:write_file(VsnRel, StartFile),
     ok = file:change_mode(VsnRel, 8#777),
     ok = file:write_file(BareRel, StartFile),
@@ -275,7 +281,7 @@ get_code_paths(Release, OutDir) ->
                         rcl_app_info:vsn_as_string(App), "ebin"]) ||
         App <- rcl_release:application_details(Release)].
 
-bin_file_contents(RelName, RelVsn, ErtsVsn) ->
+bin_file_contents(RelName, RelVsn, ErtsVsn, ErlOpts) ->
     [<<"#!/bin/sh
 
 set -e
@@ -286,6 +292,7 @@ REL_NAME=">>, RelName, <<"
 REL_VSN=">>, RelVsn, <<"
 ERTS_VSN=">>, ErtsVsn, <<"
 REL_DIR=$RELEASE_ROOT_DIR/releases/$REL_NAME-$REL_VSN
+ERL_OPTS=">>, ErlOpts, <<"
 
 ERTS_DIR=
 SYS_CONFIG=
@@ -324,6 +331,4 @@ export EMU=beam
 export PROGNAME=erl
 export LD_LIBRARY_PATH=$ERTS_DIR/lib
 
-
-
-$BINDIR/erlexec $SYS_CONFIG -boot $REL_DIR/$REL_NAME $@">>].
+$BINDIR/erlexec $ERL_OPTS $SYS_CONFIG -boot $REL_DIR/$REL_NAME $@">>].
diff --git a/src/rcl_prv_config.erl b/src/rcl_prv_config.erl
index 7a1cd19..ee1c770 100644
--- a/src/rcl_prv_config.erl
+++ b/src/rcl_prv_config.erl
@@ -82,7 +82,8 @@ load_terms({add_providers, Providers0}, {ok, State0}) ->
             ExistingProviders = rcl_state:providers(State1),
             {ok, rcl_state:providers(State1, ExistingProviders ++ Providers3)}
     end;
-
+load_terms({overrides, Overrides0}, {ok, State0}) ->
+    {ok, rcl_state:overrides(State0, Overrides0)};
 load_terms({release, {RelName, Vsn}, Applications}, {ok, State0}) ->
     Release0 = rcl_release:new(RelName, Vsn),
     case rcl_release:goals(Release0, Applications) of
diff --git a/src/rcl_prv_discover.erl b/src/rcl_prv_discover.erl
index 23a3937..0a12d24 100644
--- a/src/rcl_prv_discover.erl
+++ b/src/rcl_prv_discover.erl
@@ -49,16 +49,28 @@ do(State) ->
                           ["Resolving OTP Applications from directories:\n",
                            [[rcl_util:indent(1), LibDir, "\n"] || LibDir <- LibDirs]]
                   end),
+    resolve_app_metadata(State, LibDirs, OutputDir).
 
+-spec format_error([ErrorDetail::term()]) -> iolist().
+format_error(ErrorDetails)
+  when erlang:is_list(ErrorDetails) ->
+    [[format_detail(ErrorDetail), "\n"] || ErrorDetail <- ErrorDetails].
+
+%%%===================================================================
+%%% Internal Functions
+%%%===================================================================
+resolve_app_metadata(State, LibDirs, OutputDir) ->
     AppMeta0 = lists:flatten(ec_plists:map(fun(LibDir) ->
                                                discover_dir([OutputDir],
                                                             LibDir)
                                            end, LibDirs)),
+    AppMeta1 = setup_overrides(State, AppMeta0),
+
     Errors = [case El of
                   {error, Ret} -> Ret;
                   _ -> El
               end
-              || El <- AppMeta0,
+              || El <- AppMeta1,
                  case El of
                      {error, _} ->
                          true;
@@ -66,30 +78,38 @@ do(State) ->
                          false
                  end],
 
-    lists:filter(fun({error, _}) -> true;
-                    (_) -> false
-                 end, AppMeta0),
     case Errors of
         [] ->
-            AppMeta1 = lists:flatten(AppMeta0),
+            AppMeta2 = lists:flatten(AppMeta1),
             rcl_log:debug(rcl_state:log(State),
                           fun() ->
                                   ["Resolved the following OTP Applications from the system: \n",
-                                   [[rcl_app_info:format(1, App), "\n"] || App <- AppMeta1]]
+                                   [[rcl_app_info:format(1, App), "\n"] || App <- AppMeta2]]
                           end),
-            {ok, rcl_state:available_apps(State, AppMeta1)};
+            {ok, rcl_state:available_apps(State, AppMeta2)};
         _ ->
             ?RCL_ERROR(Errors)
     end.
 
--spec format_error([ErrorDetail::term()]) -> iolist().
-format_error(ErrorDetails)
-  when erlang:is_list(ErrorDetails) ->
-    [[format_detail(ErrorDetail), "\n"] || ErrorDetail <- ErrorDetails].
+app_name({error, _}) ->
+    undefined;
+app_name(AppMeta) ->
+    rcl_app_info:name(AppMeta).
+
+setup_overrides(State, AppMetas0) ->
+    Overrides = rcl_state:overrides(State),
+    AppMetas1 = [AppMeta || AppMeta <- AppMetas0,
+                            not lists:keymember(app_name(AppMeta), 1, Overrides)],
+    [case is_valid_otp_app(filename:join([FileName, "ebin",
+                                         erlang:atom_to_list(AppName) ++ ".app"])) of
+         [] ->
+             {error, {invalid_override, AppName, FileName}};
+         Error = {error, _} ->
+             Error;
+         App ->
+             rcl_app_info:link(App, true)
+     end || {AppName, FileName} <- Overrides] ++ AppMetas1.
 
-%%%===================================================================
-%%% Internal Functions
-%%%===================================================================
 get_lib_dirs(State) ->
     LibDirs0 = rcl_state:lib_dirs(State),
     add_rebar_deps_dir(State, LibDirs0).
@@ -133,6 +153,9 @@ add_system_lib_dir(State, LibDirs) ->
     end.
 
 -spec format_detail(ErrorDetail::term()) -> iolist().
+format_detail({error, {invalid_override, AppName, FileName}}) ->
+    io_lib:format("Override {~p, ~p} is not a valid OTP App. Perhaps you forgot to build it?",
+                  [AppName, FileName]);
 format_detail({accessing, File, eaccess}) ->
     io_lib:format("permission denied accessing file ~s", [File]);
 format_detail({accessing, File, Type}) ->
@@ -172,7 +195,7 @@ discover_dir(IgnoreDirs, File) ->
             is_valid_otp_app(File)
     end.
 
--spec is_valid_otp_app(file:name()) -> [rcl_app_info:t() | {error, Reason::term()} | []].
+-spec is_valid_otp_app(file:name()) -> rcl_app_info:t() | {error, Reason::term()} | [].
 is_valid_otp_app(File) ->
     %% Is this an ebin dir?
     EbinDir = filename:dirname(File),
diff --git a/src/rcl_state.erl b/src/rcl_state.erl
index 46c91c7..7397e6f 100644
--- a/src/rcl_state.erl
+++ b/src/rcl_state.erl
@@ -27,6 +27,8 @@
          log/1,
          output_dir/1,
          lib_dirs/1,
+         overrides/1,
+         overrides/2,
          goals/1,
          config_files/1,
          providers/1,
@@ -64,6 +66,7 @@
                   available_apps = [] :: [rcl_app_info:t()],
                   default_release :: {rcl_release:name(), rcl_release:vsn()},
                   sys_config :: file:filename() | undefined,
+                  overrides :: [{AppName::atom(), Directory::file:filename()}],
                   releases :: ec_dictionary:dictionary({ReleaseName::atom(),
                                                         ReleaseVsn::string()},
                                                        rcl_release:t()),
@@ -96,10 +99,21 @@ new(PropList, Targets) when erlang:is_list(PropList) ->
                  providers = [],
                  releases=ec_dictionary:new(ec_dict),
                  config_values=ec_dictionary:new(ec_dict),
+                 overrides = proplists:get_value(overrides, PropList, []),
                  default_release={proplists:get_value(relname, PropList, undefined),
                                   proplists:get_value(relvsn, PropList, undefined)}},
     create_logic_providers(State0).
 
+%% @doc the application overrides for the system
+-spec overrides(t()) -> [{AppName::atom(), Directory::file:filename()}].
+overrides(#state_t{overrides=Overrides}) ->
+    Overrides.
+
+%% @doc the application overrides for the system
+-spec overrides(t(), [{AppName::atom(), Directory::file:filename()}]) -> t().
+overrides(State, Overrides) ->
+    State#state_t{overrides=Overrides}.
+
 %% @doc get the current log state for the system
 -spec log(t()) -> rcl_log:t().
 log(#state_t{log=LogState}) ->
diff --git a/src/relcool.erl b/src/relcool.erl
index 44debc9..0d75c62 100644
--- a/src/relcool.erl
+++ b/src/relcool.erl
@@ -22,6 +22,7 @@
 
 -export([main/1,
          do/7,
+         do/8,
          format_error/1,
          opt_spec_list/0]).
 
@@ -59,15 +60,30 @@ main(Args) ->
 %% @param OutputDir - The directory where the release should be built to
 %% @param Configs - The list of config files for the system
 do(RelName, RelVsn, Goals, LibDirs, LogLevel, OutputDir, Configs) ->
+    do(RelName, RelVsn, Goals, LibDirs, LogLevel, OutputDir, [], Configs).
+
+%% @doc provides an API to run the Relcool process from erlang applications
+%%
+%% @param RelName - The release name to build (maybe `undefined`)
+%% @param RelVsn - The release version to build (maybe `undefined`)
+%% @param Goals - The release goals for the system in depsolver or Relcool goal
+%% format
+%% @param LibDirs - The library dirs that should be used for the system
+%% @param OutputDir - The directory where the release should be built to
+%% @param Overrides - A list of overrides for the system
+%% @param Configs - The list of config files for the system
+do(RelName, RelVsn, Goals, LibDirs, LogLevel, OutputDir, Overrides, Configs) ->
     State = rcl_state:new([{relname, RelName},
                            {relvsn, RelVsn},
                            {goals, Goals},
+                           {overrides, Overrides},
                            {output_dir, OutputDir},
                            {lib_dirs, LibDirs},
                            {log, rcl_log:new(LogLevel)}],
                           Configs),
     run_relcool_process(rcl_state:caller(State, api)).
 
+
 -spec opt_spec_list() -> [getopt:option_spec()].
 opt_spec_list() ->
     [
@@ -112,14 +128,17 @@ run_providers(State0) ->
         {ok, State1} ->
             Providers = rcl_state:providers(State1),
             Result = run_providers(ConfigProvider, Providers, State1),
-            case rcl_state:caller(State1) of
-                command_line ->
-                    init:stop(0);
-                api ->
-                    Result
-            end
+            handle_output(State1, rcl_state:caller(State1), Result)
     end.
 
+handle_output(State, command_line, E={error, _}) ->
+    report_error(State, E),
+    init:stop(127);
+handle_output(_State, command_line, _) ->
+    init:stop(0);
+handle_output(_State, api, Result) ->
+    Result.
+
 run_providers(ConfigProvider, Providers, State0) ->
     case Providers of
         [ConfigProvider | Rest] ->
@@ -135,10 +154,13 @@ run_providers(ConfigProvider, Providers, State0) ->
 run_provider(_Provider, Error = {error, _}) ->
     Error;
 run_provider(Provider, {ok, State0}) ->
+    rcl_log:debug(rcl_state:log(State0), "Running provider ~p~n",
+                  [rcl_provider:impl(Provider)]),
     case rcl_provider:do(Provider, State0) of
         {ok, State1} ->
             {ok, State1};
         E={error, _} ->
+
             E
     end.
 
diff --git a/test/rclt_release_SUITE.erl b/test/rclt_release_SUITE.erl
index 7cdf362..c13672a 100644
--- a/test/rclt_release_SUITE.erl
+++ b/test/rclt_release_SUITE.erl
@@ -24,10 +24,12 @@
          end_per_suite/1,
          init_per_testcase/2,
          all/0,
-         make_release/1]).
+         make_release/1,
+         make_overridden_release/1]).
 
 -include_lib("common_test/include/ct.hrl").
 -include_lib("eunit/include/eunit.hrl").
+-include_lib("kernel/include/file.hrl").
 
 suite() ->
     [{timetrap,{seconds,30}}].
@@ -47,7 +49,7 @@ init_per_testcase(_, Config) ->
      {state, State} | Config].
 
 all() ->
-    [make_release].
+    [make_release, make_overridden_release].
 
 make_release(Config) ->
     LibDir1 = proplists:get_value(lib1, Config),
@@ -84,6 +86,58 @@ make_release(Config) ->
     ?assert(lists:member({goal_app_2, "0.0.1"}, AppSpecs)),
     ?assert(lists:member({lib_dep_1, "0.0.1", load}, AppSpecs)).
 
+
+make_overridden_release(Config) ->
+    DataDir = proplists:get_value(data_dir, Config),
+    OverrideDir1 = filename:join([DataDir, create_random_name("override_dir_")]),
+    LibDir1 = proplists:get_value(lib1, Config),
+    [(fun({Name, Vsn}) ->
+              create_app(LibDir1, Name, Vsn, [kernel, stdlib], [])
+      end)(App)
+     ||
+        App <-
+            [{create_random_name("lib_app1_"), create_random_vsn()}
+             || _ <- lists:seq(1, 100)]],
+    OverrideApp = create_random_name("override_app"),
+    OverrideVsn = create_random_vsn(),
+    OverrideAppDir = filename:join(OverrideDir1, OverrideApp),
+    OverrideAppName = erlang:list_to_atom(OverrideApp),
+
+    create_app(LibDir1, "goal_app_1", "0.0.1", [stdlib,kernel,non_goal_1], []),
+    create_app(LibDir1, "lib_dep_1", "0.0.1", [stdlib,kernel], []),
+    create_app(LibDir1, "goal_app_2", "0.0.1", [stdlib,kernel,goal_app_1,non_goal_2], []),
+    create_app(LibDir1, "non_goal_1", "0.0.1", [stdlib,kernel], [lib_dep_1]),
+    create_app(LibDir1, "non_goal_2", "0.0.1", [stdlib,kernel], []),
+
+    create_app(OverrideDir1, OverrideApp, OverrideVsn, [stdlib,kernel], []),
+
+    ConfigFile = filename:join([LibDir1, "relcool.config"]),
+    write_config(ConfigFile,
+                 [{release, {foo, "0.0.1"},
+                   [goal_app_1,
+                    erlang:list_to_atom(OverrideApp),
+                    goal_app_2]}]),
+    OutputDir = filename:join([proplists:get_value(data_dir, Config),
+                               create_random_name("relcool-output")]),
+    {ok, State} = relcool:do(undefined, undefined, [], [LibDir1], 2,
+                              OutputDir, [{OverrideAppName, OverrideAppDir}],
+                             [ConfigFile]),
+    [{{foo, "0.0.1"}, Release}] = ec_dictionary:to_list(rcl_state:releases(State)),
+    AppSpecs = rcl_release:applications(Release),
+    ?assert(lists:keymember(stdlib, 1, AppSpecs)),
+    ?assert(lists:keymember(kernel, 1, AppSpecs)),
+    ?assert(lists:member({non_goal_1, "0.0.1"}, AppSpecs)),
+    ?assert(lists:member({non_goal_2, "0.0.1"}, AppSpecs)),
+    ?assert(lists:member({goal_app_1, "0.0.1"}, AppSpecs)),
+    ?assert(lists:member({goal_app_2, "0.0.1"}, AppSpecs)),
+    ?assert(lists:member({OverrideAppName, OverrideVsn}, AppSpecs)),
+    ?assert(lists:member({lib_dep_1, "0.0.1", load}, AppSpecs)),
+    {ok, Real} = file:read_link(filename:join([OutputDir, "lib",
+                                               OverrideApp ++ "-" ++ OverrideVsn])),
+    ?assertMatch(OverrideAppDir, Real).
+
+
+
 %%%===================================================================
 %%% Helper Functions
 %%%===================================================================