Merge branch 'master' into feature-git-worktree-193

15 files changed, 321 insertions, 190 deletions

diff --git a/.travis.yml b/.travis.yml
index 79ebf42..75c3c0e 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -22,6 +22,9 @@ python:
 - '3.4'
 - '3.5'
 - '3.6'
+- '3.7'
+- '3.8-dev'
+dist: xenial  # needed for 3.7+
 env:
 - TOXENV=py-test
 
@@ -62,40 +65,28 @@ jobs:
         <<: *pypi
         distributions: "sdist bdist_wheel"
 
-    - <<: *deploy
+    - &bdist_egg
+      <<: *deploy
       name: "python eggs 2.7"
       python: '2.7'
       deploy:
         <<: *pypi
         distributions: "bdist_egg"
-    - <<: *deploy
+    - <<: *bdist_egg
       name: "python eggs 3.4"
       python: '3.4'
-      deploy:
-        <<: *pypi
-        distributions: "bdist_egg"
-
-
-    - <<: *deploy
+    - <<: *bdist_egg
       name: "python eggs 3.5"
       python: '3.5'
-      deploy:
-        <<: *pypi
-        distributions: "bdist_egg"
-
-    - <<: *deploy
+    - <<: *bdist_egg
       name: "python eggs 3.6"
       python: '3.6'
-      deploy:
-        <<: *pypi
-        distributions: "bdist_egg"
-
-    # - <<: *eggs
-    #   name: "python eggs 3.7"
-    #   python: '3.7'
-    #  deploy:
-    #    <<: *pypi
-    #    distributions: "bdist_egg"
+    - <<: *bdist_egg
+      name: "python eggs 3.7"
+      python: '3.7'
+    - <<: *bdist_egg
+      name: "python eggs 3.8"
+      python: '3.8-dev'
 
 cache:
   directories:
diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index f0b299d..c6a1968 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -1,3 +1,27 @@
+* fix #305 - ensure the git file finder closes filedescriptors even when errors happen
+
+v3.3.3
+======
+
+* add eggs  for python3.7 and 3.8 to the deploy
+
+v3.3.2
+======
+
+
+* fix #335 - fix python3.8 support and add builds for up to python3.8
+
+v3.3.1
+======
+
+* fix #333 (regression from #198) - use a specific fallback root when calling fallbacks. Remove old
+  hack that resets the root when fallback entrypoints are present.
+
+v3.3.0
+======
+
+* fix #198 by adding the ``fallback_version`` option, which sets the version to be used when everything else fails.
+
 v3.2.0
 ======
 
diff --git a/README.rst b/README.rst
index dc7a4d7..9f6f105 100644
--- a/README.rst
+++ b/README.rst
@@ -1,61 +1,119 @@
 setuptools_scm
 ===============
 
-:code:`setuptools_scm` handles managing your python package versions
-in scm metadata instead of declaring them as the version argument
-or in a scm managed file.
+``setuptools_scm`` handles managing your Python package versions
+in SCM metadata instead of declaring them as the version argument
+or in a SCM managed file.
 
-It also handles file finders for the supported scm's.
+It also handles file finders for the supported SCMs.
 
 .. image:: https://travis-ci.org/pypa/setuptools_scm.svg?branch=master
     :target: https://travis-ci.org/pypa/setuptools_scm
 
-Setup.py usage
---------------
+``setup.py`` usage
+------------------
+
+To use ``setuptools_scm`` just modify your project's ``setup.py`` file
+like this:
+
+* Add ``setuptools_scm`` to the ``setup_requires`` parameter.
+* Add the ``use_scm_version`` parameter and set it to ``True``.
+
+For example:
+
+.. code:: python
+
+    from setuptools import setup
+    setup(
+        ...,
+        use_scm_version=True,
+        setup_requires=['setuptools_scm'],
+        ...,
+    )
 
-To use setuptools_scm just modify your project's setup.py file like this:
+Arguments to ``get_version()`` (see below) may be passed as a dictionary to
+``use_scm_version``. For example:
 
-1. Add :code:`'setuptools_scm'` to the :code:`setup_requires` parameter
-2. Add the :code:`use_scm_version` parameter and set it to ``True``
+.. code:: python
 
-   E.g.:
+    from setuptools import setup
+    setup(
+        ...,
+        use_scm_version = {"root": "..", "relative_to": __file__},
+        setup_requires=['setuptools_scm'],
+        ...,
+    )
 
-   .. code:: python
+Once configured, you can access the version number in your package via
+``pkg_resources`` (`PEP-0396 <https://www.python.org/dev/peps/pep-0396>`_). For
+example:
 
-       from setuptools import setup
-       setup(
-           ...,
-           use_scm_version=True,
-           setup_requires=['setuptools_scm'],
-           ...,
-       )
+.. code:: python
 
-   Arguments to ``get_version()`` (see below) may be passed as a
-   dictionary to ``use_scm_version``. For example:
+   from pkg_resources import get_distribution, DistributionNotFound
+   try:
+       __version__ = get_distribution(__name__).version
+   except DistributionNotFound:
+       # package is not installed
+       pass
 
-   .. code:: python
+You can also confirm the version number locally via ``setup.py``:
 
-       from setuptools import setup
-       setup(
-           ...,
-           use_scm_version = {"root": "..", "relative_to": __file__},
-           setup_requires=['setuptools_scm'],
-           ...,
-       )
+.. code-block:: shell
 
+    $ python setup.py --version
 
-3. Access the version number in your package via :code:`pkg_resources`
+.. note::
 
-   E.g. (`PEP-0396 <https://www.python.org/dev/peps/pep-0396>`_):
+   If you see unusual version numbers for packages but ``python setup.py
+   --version`` reports the expected version number, ensure ``[egg_info]`` is
+   not defined in ``setup.cfg``.
 
-   .. code:: python
 
-      from pkg_resources import get_distribution, DistributionNotFound
-      try:
-          __version__ = get_distribution(__name__).version
-      except DistributionNotFound:
-          # package is not installed
-          pass
+``setup.cfg``
+-------------
+
+If using `setuptools 30.3.0
+<https://setuptools.readthedocs.io/en/latest/setuptools.html#configuring-setup-using-setup-cfg-files>`_
+or greater, you can store ``setup_requires`` configuration in ``setup.cfg``.
+However, ``use_scm_version`` must still be placed in ``setup.py``. For example:
+
+.. code:: python
+
+    # setup.py
+    from setuptools import setup
+    setup(
+        use_scm_version=True,
+    )
+
+.. code:: ini
+
+    # setup.cfg
+    [metadata]
+    ...
+
+    [options]
+    setup_requires =
+      setuptools_scm
+    ...
+
+.. important::
+
+    Ensure neither the ``[metadata]`` ``version`` option nor the ``[egg_info]``
+    section are defined, as these will interfere with ``setuptools_scm``.
+
+You may also need to define a ``pyproject.toml`` file (`PEP-0518
+<https://www.python.org/dev/peps/pep-0518>`_) to ensure you have the required
+version of ``setuptools``:
+
+.. code:: ini
+
+    # pyproject.toml
+    [build-system]
+    requires = ["setuptools>=30.3.0", "wheel", "setuptools_scm"]
+
+For more information, refer to the `setuptools issue #1002
+<https://github.com/pypa/setuptools/issues/1002>`_.
 
 
 Programmatic usage
@@ -69,13 +127,13 @@ than the project's root, you can use:
     from setuptools_scm import get_version
     version = get_version(root='..', relative_to=__file__)
 
-See `setup.py Usage`_ above for how to use this within setup.py.
+See `setup.py Usage`_ above for how to use this within ``setup.py``.
 
 
-Usage from sphinx
+Usage from Sphinx
 -----------------
 
-It is discouraged to use setuptools_scm from sphinx itself,
+It is discouraged to use ``setuptools_scm`` from Sphinx itself,
 instead use ``pkg_resources`` after editable/real installation:
 
 .. code:: python
@@ -86,25 +144,24 @@ instead use ``pkg_resources`` after editable/real installation:
     # for example take major/minor
     version = '.'.join(release.split('.')[:2])
 
-The underlying reason is, that services like readthedocs sometimes change
-the workingdirectory for good reasons and using the installed metadata prevents
-using needless volatile data there.
+The underlying reason is, that services like *Read the Docs* sometimes change
+the working directory for good reasons and using the installed metadata
+prevents using needless volatile data there.
 
 Notable Plugins
 ----------------
 
 `setuptools_scm_git_archive <https://pypi.python.org/pypi/setuptools_scm_git_archive>`_
-provides partial support for obtaining versions from git archives
-that belong to tagged versions. The only reason for not including
-it in setuptools-scm itself is git/github not supporting
-sufficient metadata for untagged/followup commits,
-which is preventing a consistent UX.
+    Provides partial support for obtaining versions from git archives that
+    belong to tagged versions. The only reason for not including it in
+    ``setuptools_scm`` itself is Git/GitHub not supporting sufficient metadata
+    for untagged/followup commits, which is preventing a consistent UX.
 
 
 Default versioning scheme
 --------------------------
 
-In the standard configuration setuptools_scm takes a look at 3 things:
+In the standard configuration ``setuptools_scm`` takes a look at three things:
 
 1. latest tag (with a version number)
 2. the distance to this tag (e.g. number of revisions since latest tag)
@@ -112,19 +169,19 @@ In the standard configuration setuptools_scm takes a look at 3 things:
 
 and uses roughly the following logic to render the version:
 
-:code:`no distance and clean`:
-    :code:`{tag}`
-:code:`distance and clean`:
-    :code:`{next_version}.dev{distance}+{scm letter}{revision hash}`
-:code:`no distance and not clean`:
-    :code:`{tag}+dYYYMMMDD`
-:code:`distance and not clean`:
-    :code:`{next_version}.dev{distance}+{scm letter}{revision hash}.dYYYMMMDD`
+no distance and clean:
+    ``{tag}``
+distance and clean:
+    ``{next_version}.dev{distance}+{scm letter}{revision hash}``
+no distance and not clean:
+    ``{tag}+dYYYMMMDD``
+distance and not clean:
+    ``{next_version}.dev{distance}+{scm letter}{revision hash}.dYYYMMMDD``
 
-The next version is calculated by adding ``1`` to the last numeric component
-of the tag.
+The next version is calculated by adding ``1`` to the last numeric component of
+the tag.
 
-For git projects, the version relies on `git describe <https://git-scm.com/docs/git-describe>`_,
+For Git projects, the version relies on `git describe <https://git-scm.com/docs/git-describe>`_,
 so you will see an additional ``g`` prepended to the ``{revision hash}``.
 
 Semantic Versioning (SemVer)
@@ -132,30 +189,30 @@ Semantic Versioning (SemVer)
 
 Due to the default behavior it's necessary to always include a
 patch version (the ``3`` in ``1.2.3``), or else the automatic guessing
-will increment the wrong part of the semver (e.g. tag ``2.0`` results in
+will increment the wrong part of the SemVer (e.g. tag ``2.0`` results in
 ``2.1.devX`` instead of ``2.0.1.devX``). So please make sure to tag
 accordingly.
 
 .. note::
 
-    Future versions of setuptools_scm will switch to
-    `SemVer <http://semver.org/>`_ by default hiding the the old behavior
-    as an configurable option.
+    Future versions of ``setuptools_scm`` will switch to `SemVer
+    <http://semver.org/>`_ by default hiding the the old behavior as an
+    configurable option.
 
 
 Builtin mechanisms for obtaining version numbers
 --------------------------------------------------
 
-1. the scm itself (git/hg)
-2. :code:`.hg_archival` files (mercurial archives)
-3. PKG-INFO
+1. the SCM itself (git/hg)
+2. ``.hg_archival`` files (mercurial archives)
+3. ``PKG-INFO``
 
 .. note::
 
-    git archives are not supported due to git shortcomings
+    Git archives are not supported due to Git shortcomings
 
 
-Configuration Parameters
+Configuration parameters
 ------------------------
 
 In order to configure the way ``use_scm_version`` works you can provide
@@ -164,21 +221,21 @@ a mapping with options instead of a boolean value.
 The currently supported configuration keys are:
 
 :root:
-    Relative path to cwd, used for finding the scm root, defaults to :code:`.`
+    Relative path to cwd, used for finding the SCM root; defaults to ``.``
 
 :version_scheme:
-    Configures how the local version number is constructed.
-    Either an entrypoint name or a callable.
+    Configures how the local version number is constructed; either an
+    entrypoint name or a callable.
 
 :local_scheme:
-    Configures how the local component of the version is constructed.
-    Either an entrypoint name or a callable.
+    Configures how the local component of the version is constructed; either an
+    entrypoint name or a callable.
 
 :write_to:
     A path to a file that gets replaced with a file containing the current
-    version.  It is ideal for creating a version.py file within the package,
-    typically used to avoid using `pkg_resources.get_distribution` (which adds
-    some overhead).
+    version. It is ideal for creating a ``version.py`` file within the
+    package, typically used to avoid using `pkg_resources.get_distribution`
+    (which adds some overhead).
 
     .. warning::
 
@@ -188,38 +245,44 @@ The currently supported configuration keys are:
 
 :write_to_template:
     A newstyle format string that is given the current version as
-    the :code:`version` keyword argument for formatting.
+    the ``version`` keyword argument for formatting.
 
 :relative_to:
     A file from which the root can be resolved.
     Typically called by a script or module that is not in the root of the
-    repository to point setuptools_scm at the root of the repository by
+    repository to point ``setuptools_scm`` at the root of the repository by
     supplying ``__file__``.
 
-:parse:
-  A function that will be used instead of the discovered SCM for parsing the
-  version.
-  Use with caution, this is a function for advanced use, and you should be
-  familiar with the setuptools_scm internals to use it.
-
 :tag_regex:
-  A python regex string to extract the version part from any SCM tag.
-  The regex needs to contain three named groups prefix, version and suffix,
-  where `version` captures the actual version information.
+    A Python regex string to extract the version part from any SCM tag.
+    The regex needs to contain three named groups prefix, version and suffix,
+    where ``version`` captures the actual version information.
 
-  defaults to the value of ``setuptools_scm.config.DEFAULT_TAG_REGEX``
-  (see `config.py <src/setuptools_scm/config.py>`_).
+    Defaults to the value of ``setuptools_scm.config.DEFAULT_TAG_REGEX``
+    (see `config.py <src/setuptools_scm/config.py>`_).
+
+:fallback_version:
+    A version string that will be used if no other method for detecting the
+    version worked (e.g., when using a tarball with no metadata).  If this is
+    unset (the default), setuptools_scm will error if it fails to detect the
+    version.
+
+:parse:
+    A function that will be used instead of the discovered SCM for parsing the
+    version.
+    Use with caution, this is a function for advanced use, and you should be
+    familiar with the ``setuptools_scm`` internals to use it.
 
 :git_describe_command:
-  This command will be used instead the default `git describe` command.
-  Use with caution, this is a function for advanced use, and you should be
-  familiar with the setuptools_scm internals to use it.
+    This command will be used instead the default ``git describe`` command.
+    Use with caution, this is a function for advanced use, and you should be
+    familiar with the ``setuptools_scm`` internals to use it.
 
-  The default value is set by ``setuptools_scm.git.DEFAULT_DESCRIBE``
-  (see `git.py <src/setuptools_scm/git.py>`_).
+    Defaults to the value set by ``setuptools_scm.git.DEFAULT_DESCRIBE``
+    (see `git.py <src/setuptools_scm/git.py>`_).
 
-To use setuptools_scm in other Python code you can use the
-``get_version`` function:
+To use ``setuptools_scm`` in other Python code you can use the ``get_version``
+function:
 
 .. code:: python
 
@@ -229,13 +292,12 @@ To use setuptools_scm in other Python code you can use the
 It optionally accepts the keys of the ``use_scm_version`` parameter as
 keyword arguments.
 
-Example configuration in `setup.py` format:
+Example configuration in ``setup.py`` format:
 
 .. code:: python
 
     from setuptools import setup
 
-
     setup(
         use_scm_version={
             'write_to': 'version.txt',
@@ -243,51 +305,52 @@ Example configuration in `setup.py` format:
         }
     )
 
-Environment Variables
+Environment variables
 ---------------------
 
 :SETUPTOOLS_SCM_PRETEND_VERSION:
-  when defined and not empty,
-  its used as the primary source for the version number
-  in which case it will be a unparsed string
+    when defined and not empty,
+    its used as the primary source for the version number
+    in which case it will be a unparsed string
+
 :SETUPTOOLS_SCM_DEBUG:
-  when defined and not empty,
-  a lot of debug information will be printed as part of setuptools_scm operating
+    when defined and not empty,
+    a lot of debug information will be printed as part of ``setuptools_scm``
+    operating
 
 Extending setuptools_scm
 ------------------------
 
-setuptools_scm ships with a few setuptools entrypoints based hooks to extend
-its default capabilities.
+``setuptools_scm`` ships with a few ``setuptools`` entrypoints based hooks to
+extend its default capabilities.
 
 Adding a new SCM
 ~~~~~~~~~~~~~~~~
 
-setuptools_scm provides 2 entrypoints for adding new SCMs
+``setuptools_scm`` provides two entrypoints for adding new SCMs:
 
 ``setuptools_scm.parse_scm``
     A function used to parse the metadata of the current workdir
     using the name of the control directory/file of your SCM as the
     entrypoint's name. E.g. for the built-in entrypoint for git the
-    entrypoint is named :code:`.git` and references
-    :code:`'setuptools_scm.git:parse'`.
+    entrypoint is named ``.git`` and references ``setuptools_scm.git:parse``
 
-    The return value MUST be a :code:`setuptools.version.ScmVersion` instance
-    created by the function :code:`setuptools_scm.version:meta`.
+  The return value MUST be a ``setuptools.version.ScmVersion`` instance
+  created by the function ``setuptools_scm.version:meta``.
 
 ``setuptools_scm.files_command``
-    Either a string containing a shell command that prints all SCM managed
-    files in its current working directory or a callable, that given a
-    pathname will return that list.
+  Either a string containing a shell command that prints all SCM managed
+  files in its current working directory or a callable, that given a
+  pathname will return that list.
 
-    Also use then name of your SCM control directory as name of the entrypoint.
+  Also use then name of your SCM control directory as name of the entrypoint.
 
 Version number construction
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
 ``setuptools_scm.version_scheme``
     Configures how the version number is constructed given a
-    :code:`setuptools.version.ScmVersion` instance and should return a string
+    ``setuptools.version.ScmVersion`` instance and should return a string
     representing the version.
 
     Available implementations:
@@ -297,25 +360,25 @@ Version number construction
 
 ``setuptools_scm.local_scheme``
     Configures how the local part of a version is rendered given a
-    :code:`setuptools.version.ScmVersion` instance and should return a string
+    ``setuptools.version.ScmVersion`` instance and should return a string
     representing the local version.
 
     Available implementations:
 
     :node-and-date: adds the node on dev versions and the date on dirty
                     workdir (default)
-    :node-and-timestamp: like :code:`node-and-date` but with a timestamp of
-                         the form :code:`{:%Y%m%d%H%M%S}` instead
-    :dirty-tag: adds :code:`+dirty` if the current workdir has changes
+    :node-and-timestamp: like ``node-and-date`` but with a timestamp of
+                         the form ``{:%Y%m%d%H%M%S}`` instead
+    :dirty-tag: adds ``+dirty`` if the current workdir has changes
 
 
-Importing in setup.py
-~~~~~~~~~~~~~~~~~~~~~
+Importing in ``setup.py``
+~~~~~~~~~~~~~~~~~~~~~~~~~
 
-To support usage in :code:`setup.py` passing a callable into use_scm_version
+To support usage in ``setup.py`` passing a callable into ``use_scm_version``
 is supported.
 
-Within that callable, setuptools_scm is available for import.
+Within that callable, ``setuptools_scm`` is available for import.
 The callable must return the configuration.
 
 
@@ -354,8 +417,8 @@ some environments require a test prior to install,
 Code of Conduct
 ---------------
 
-Everyone interacting in the setuptools_scm project's codebases, issue trackers,
-chat rooms, and mailing lists is expected to follow the
+Everyone interacting in the ``setuptools_scm`` project's codebases, issue
+trackers, chat rooms, and mailing lists is expected to follow the
 `PyPA Code of Conduct`_.
 
 .. _PyPA Code of Conduct: https://www.pypa.io/en/latest/code-of-conduct/
diff --git a/setup.py b/setup.py
index d38527a..2eb533b 100644
--- a/setup.py
+++ b/setup.py
@@ -76,6 +76,7 @@ arguments = dict(
         .hg_archival.txt = setuptools_scm.hg:parse_archival
         PKG-INFO = setuptools_scm.hacks:parse_pkginfo
         pip-egg-info = setuptools_scm.hacks:parse_pip_egg_info
+        setup.py = setuptools_scm.hacks:fallback_version
 
         [setuptools_scm.files_command]
         .hg = setuptools_scm.file_finder_hg:hg_find_files
@@ -103,6 +104,7 @@ arguments = dict(
         "Programming Language :: Python :: 3.4",
         "Programming Language :: Python :: 3.5",
         "Programming Language :: Python :: 3.6",
+        "Programming Language :: Python :: 3.7",
         "Topic :: Software Development :: Libraries",
         "Topic :: Software Development :: Version Control",
         "Topic :: System :: Software Distribution",
diff --git a/src/setuptools_scm/__init__.py b/src/setuptools_scm/__init__.py
index f49cce4..f3886ed 100644
--- a/src/setuptools_scm/__init__.py
+++ b/src/setuptools_scm/__init__.py
@@ -31,12 +31,12 @@ def version_from_scm(root):
     config = Configuration()
     config.root = root
     # TODO: Is it API?
-    return _version_from_entrypoint(config, "setuptools_scm.parse_scm")
+    return _version_from_entrypoints(config)
 
 
-def _call_entrypoint_fn(config, fn):
+def _call_entrypoint_fn(root, config, fn):
     if function_has_arg(fn, "config"):
-        return fn(config.absolute_root, config=config)
+        return fn(root, config=config)
     else:
         warnings.warn(
             "parse functions are required to provide a named argument"
@@ -44,12 +44,18 @@ def _call_entrypoint_fn(config, fn):
             category=PendingDeprecationWarning,
             stacklevel=2,
         )
-        return fn(config.absolute_root)
+        return fn(root)
 
 
-def _version_from_entrypoint(config, entrypoint):
-    for ep in iter_matching_entrypoints(config.absolute_root, entrypoint):
-        version = _call_entrypoint_fn(config, ep.load())
+def _version_from_entrypoints(config, fallback=False):
+    if fallback:
+        entrypoint = "setuptools_scm.parse_scm_fallback"
+        root = config.fallback_root
+    else:
+        entrypoint = "setuptools_scm.parse_scm"
+        root = config.absolute_root
+    for ep in iter_matching_entrypoints(root, entrypoint):
+        version = _call_entrypoint_fn(root, config, ep.load())
 
         if version:
             return version
@@ -81,20 +87,16 @@ def _do_parse(config):
         return meta(tag=pretended, preformatted=True, config=config)
 
     if config.parse:
-        parse_result = _call_entrypoint_fn(config, config.parse)
+        parse_result = _call_entrypoint_fn(config.absolute_root, config, config.parse)
         if isinstance(parse_result, string_types):
             raise TypeError(
                 "version parse result was a string\nplease return a parsed version"
             )
-        version = parse_result or _version_from_entrypoint(
-            config, "setuptools_scm.parse_scm_fallback"
-        )
+        version = parse_result or _version_from_entrypoints(config, fallback=True)
     else:
         # include fallbacks after dropping them from the main entrypoint
-        version = _version_from_entrypoint(
-            config, "setuptools_scm.parse_scm"
-        ) or _version_from_entrypoint(
-            config, "setuptools_scm.parse_scm_fallback"
+        version = _version_from_entrypoints(config) or _version_from_entrypoints(
+            config, fallback=True
         )
 
     if version:
@@ -120,6 +122,8 @@ def get_version(
     write_to_template=None,
     relative_to=None,
     tag_regex=None,
+    fallback_version=None,
+    fallback_root=".",
     parse=None,
     git_describe_command=None,
 ):
@@ -132,12 +136,14 @@ def get_version(
 
     config = Configuration()
     config.root = root
+    config.fallback_root = fallback_root
     config.version_scheme = version_scheme
     config.local_scheme = local_scheme
     config.write_to = write_to
     config.write_to_template = write_to_template
     config.relative_to = relative_to
     config.tag_regex = tag_regex
+    config.fallback_version = fallback_version
     config.parse = parse
     config.git_describe_command = git_describe_command
 
diff --git a/src/setuptools_scm/config.py b/src/setuptools_scm/config.py
index 796dd0b..38f79ae 100644
--- a/src/setuptools_scm/config.py
+++ b/src/setuptools_scm/config.py
@@ -44,6 +44,7 @@ class Configuration(object):
     local_scheme = None
     write_to = None
     write_to_template = None
+    fallback_version = None
     _relative_to = None
     parse = None
     _tag_regex = None
@@ -59,11 +60,21 @@ class Configuration(object):
         self.local_scheme = "node-and-date"
         self.write_to = ""
         self.write_to_template = None
+        self.fallback_version = None
+        self.fallback_root = "."
         self.parse = None
         self.tag_regex = DEFAULT_TAG_REGEX
         self.git_describe_command = None
 
     @property
+    def fallback_root(self):
+        return self._fallback_root
+
+    @fallback_root.setter
+    def fallback_root(self, value):
+        self._fallback_root = os.path.abspath(value)
+
+    @property
     def absolute_root(self):
         return self._absolute_root
 
diff --git a/src/setuptools_scm/file_finder_git.py b/src/setuptools_scm/file_finder_git.py
index b7b55ed..5cda162 100644
--- a/src/setuptools_scm/file_finder_git.py
+++ b/src/setuptools_scm/file_finder_git.py
@@ -28,16 +28,16 @@ def _git_toplevel(path):
 
 
 def _git_interpret_archive(fd, toplevel):
-    tf = tarfile.open(fileobj=fd, mode="r|*")
-    git_files = set()
-    git_dirs = {toplevel}
-    for member in tf.getmembers():
-        name = os.path.normcase(member.name).replace("/", os.path.sep)
-        if member.type == tarfile.DIRTYPE:
-            git_dirs.add(name)
-        else:
-            git_files.add(name)
-    return git_files, git_dirs
+    with tarfile.open(fileobj=fd, mode="r|*") as tf:
+        git_files = set()
+        git_dirs = {toplevel}
+        for member in tf.getmembers():
+            name = os.path.normcase(member.name).replace("/", os.path.sep)
+            if member.type == tarfile.DIRTYPE:
+                git_dirs.add(name)
+            else:
+                git_files.add(name)
+        return git_files, git_dirs
 
 
 def _git_ls_files_and_dirs(toplevel):
@@ -46,7 +46,11 @@ def _git_ls_files_and_dirs(toplevel):
     cmd = ["git", "archive", "--prefix", toplevel + os.path.sep, "HEAD"]
     proc = subprocess.Popen(cmd, stdout=subprocess.PIPE, cwd=toplevel)
     try:
-        return _git_interpret_archive(proc.stdout, toplevel)
+        try:
+            return _git_interpret_archive(proc.stdout, toplevel)
+        finally:
+            # ensure we avoid ressource warnings by cleaning up the pocess
+            proc.wait()
     except Exception:
         if proc.wait() != 0:
             log.exception("listing git files failed - pretending there aren't any")
diff --git a/src/setuptools_scm/hacks.py b/src/setuptools_scm/hacks.py
index a4ca586..1ef0bb4 100644
--- a/src/setuptools_scm/hacks.py
+++ b/src/setuptools_scm/hacks.py
@@ -22,3 +22,8 @@ def parse_pip_egg_info(root, config=None):
     if not items:
         return
     return parse_pkginfo(os.path.join(pipdir, items[0]), config=config)
+
+
+def fallback_version(root, config=None):
+    if config.fallback_version is not None:
+        return meta(config.fallback_version, preformatted=True, config=config)
diff --git a/src/setuptools_scm/integration.py b/src/setuptools_scm/integration.py
index 737e84f..e18b3e5 100644
--- a/src/setuptools_scm/integration.py
+++ b/src/setuptools_scm/integration.py
@@ -2,7 +2,6 @@ from pkg_resources import iter_entry_points
 
 from .version import _warn_if_setuptools_outdated
 from .utils import do
-from .discover import iter_matching_entrypoints
 from . import get_version
 
 
@@ -14,12 +13,7 @@ def version_keyword(dist, keyword, value):
         value = {}
     if getattr(value, "__call__", None):
         value = value()
-    # this piece of code is a hack to counter the mistake in root finding
-    matching_fallbacks = iter_matching_entrypoints(
-        ".", "setuptools_scm.parse_scm_fallback"
-    )
-    if any(matching_fallbacks):
-        value.pop("root", None)
+
     dist.metadata.version = get_version(**value)
 
 
diff --git a/src/setuptools_scm/utils.py b/src/setuptools_scm/utils.py
index 7e4e9f5..5b59005 100644
--- a/src/setuptools_scm/utils.py
+++ b/src/setuptools_scm/utils.py
@@ -100,7 +100,8 @@ def function_has_arg(fn, argname):
     if PY2:
         argspec = inspect.getargspec(fn).args
     else:
-        argspec = inspect.getfullargspec(fn).args
+
+        argspec = inspect.signature(fn).parameters
 
     return argname in argspec
 
diff --git a/testing/conftest.py b/testing/conftest.py
index fb81953..0d34731 100644
--- a/testing/conftest.py
+++ b/testing/conftest.py
@@ -63,7 +63,7 @@ class Wd(object):
         __tracebackhide__ = True
         from setuptools_scm import get_version
 
-        version = get_version(root=str(self.cwd), **kw)
+        version = get_version(root=str(self.cwd), fallback_root=str(self.cwd), **kw)
         print(version)
         return version
 
diff --git a/testing/test_basic_api.py b/testing/test_basic_api.py
index c032d23..f342e23 100644
--- a/testing/test_basic_api.py
+++ b/testing/test_basic_api.py
@@ -1,4 +1,5 @@
 import os
+import sys
 import py
 import pytest
 
@@ -22,8 +23,9 @@ def test_data_from_mime(tmpdir):
     assert res == {"name": "test", "revision": "1"}
 
 
-def test_version_from_pkginfo(wd):
+def test_version_from_pkginfo(wd, monkeypatch):
     wd.write("PKG-INFO", "Version: 0.1")
+
     assert wd.version == "0.1"
 
     # replicate issue 167
@@ -56,6 +58,18 @@ def test_root_parameter_pass_by(monkeypatch, tmpdir):
     setuptools_scm.get_version(root=tmpdir.strpath)
 
 
+def test_fallback(tmpdir, monkeypatch):
+    monkeypatch.delenv("SETUPTOOLS_SCM_DEBUG")
+    p = tmpdir.ensure("sub/package", dir=1)
+    p.join("setup.py").write(
+        """from setuptools import setup
+setup(use_scm_version={"fallback_version": "12.34"})
+"""
+    )
+    res = do((sys.executable, "setup.py", "--version"), p)
+    assert res == "12.34"
+
+
 @pytest.mark.parametrize(
     "version", ["1.0", "1.2.3.dev1+ge871260", "1.2.3.dev15+ge871260.d20180625", "2345"]
 )
diff --git a/testing/test_git.py b/testing/test_git.py
index 1ada360..9307850 100644
--- a/testing/test_git.py
+++ b/testing/test_git.py
@@ -1,4 +1,5 @@
 import sys
+
 from setuptools_scm import integration
 from setuptools_scm.utils import do
 from setuptools_scm import git
@@ -30,6 +31,19 @@ def test_parse_describe_output(given, tag, number, node, dirty):
     assert parsed == (tag, number, node, dirty)
 
 
+def test_root_relative_to(tmpdir, wd, monkeypatch):
+    monkeypatch.delenv("SETUPTOOLS_SCM_DEBUG")
+    p = wd.cwd.ensure("sub/package", dir=1)
+    p.join("setup.py").write(
+        """from setuptools import setup
+setup(use_scm_version={"root": "../..",
+                       "relative_to": __file__})
+"""
+    )
+    res = do((sys.executable, "setup.py", "--version"), p)
+    assert res == "0.1.dev0"
+
+
 @pytest.mark.issue("https://github.com/pypa/setuptools_scm/issues/298")
 def test_file_finder_no_history(wd, caplog):
     file_list = git_find_files(str(wd.cwd))
diff --git a/testing/test_regressions.py b/testing/test_regressions.py
index 702cbf2..f3b0fc6 100644
--- a/testing/test_regressions.py
+++ b/testing/test_regressions.py
@@ -29,7 +29,7 @@ def test_pkginfo_noscmroot(tmpdir, monkeypatch):
 
     do("git init", p.dirpath())
     res = do((sys.executable, "setup.py", "--version"), p)
-    assert res == "1.0"
+    assert res == "0.1.dev0"
 
 
 def test_pip_egg_info(tmpdir, monkeypatch):
@@ -43,10 +43,10 @@ def test_pip_egg_info(tmpdir, monkeypatch):
     )
 
     with pytest.raises(LookupError):
-        get_version(root=p.strpath)
+        get_version(root=p.strpath, fallback_root=p.strpath)
 
     p.ensure("pip-egg-info/random.egg-info/PKG-INFO").write("Version: 1.0")
-    assert get_version(root=p.strpath) == "1.0"
+    assert get_version(root=p.strpath, fallback_root=p.strpath) == "1.0"
 
 
 @pytest.mark.issue(164)
diff --git a/tox.ini b/tox.ini
index 121beb5..129f9b4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -1,8 +1,10 @@
 [tox]
-envlist=py{27,34,35,36,37}-test,flake8,check_readme,py{27,36}-selfcheck
+envlist=py{27,34,35,36,37,38}-test,flake8,check_readme,py{27,37}-selfcheck
 
 [pytest]
 filterwarnings=error
+markers=
+    issue(id): reference to github issue
 
 [flake8]
 max-complexity = 10