simplify and improve version determination

The file kwant/_static_version.py is no longer written upon every
invocation of setup.py.  Instead, a file kwant/_kwant_version.py is
injected into source and binary distributions.

The static version in kwant/_kwant_version.py now takes precedence
before any version from git.  This makes the --no-git option to setup.py
no longer necessary, since the existence of kwant/_kwant_version.py has
the same role.  The motivation behind this change is to allow keeping
Kwant distributions in git repositories that have a different layout
from the canonical Kwant git repository.  This is useful for example for
packaging.

The name of the static version file was changed to avoid problems with
stale files.

.gitignore

@@ -5,7 +5,6 @@ MANIFEST
 *.so
 /kwant/*.c
 /kwant/*/*.c
-/kwant/_static_version.py
 /tutorial
 /build
 /dist

kwant/_common.py

-# Copyright 2011-2014 Kwant authors.
+# Copyright 2011-2015 Kwant authors.
 #
 # This file is part of Kwant.  It is subject to the license terms in the
 # LICENSE file found in the top-level directory of this distribution and at
@@ -56,11 +56,11 @@ def get_version_from_git():
     return version
 
 
-version = get_version_from_git()
-if version is None:
-    try:
-        from _static_version import version
-    except:
+from _kwant_version import version
+version_is_from_git = (version == "__use_git__")
+if version_is_from_git:
+    version = get_version_from_git()
+    if not version:
         version = "unknown"
 
 

kwant/_kwant_version.py

+# This file will be overwritten by setup.py when a source or binary
+# distribution is made.  The magic value "__use_git__" is interpreted by
+# _common.py in this directory.
+version = "__use_git__"

setup.py

 #!/usr/bin/env python
 
-# Copyright 2011-2013 Kwant authors.
+# Copyright 2011-2015 Kwant authors.
 #
 # This file is part of Kwant.  It is subject to the license terms in the
 # LICENSE file found in the top-level directory of this distribution and at
@@ -26,22 +26,31 @@ from distutils.command.sdist import sdist as distutils_sdist
 
 import numpy
 
-_dont_write_bytecode_saved = sys.dont_write_bytecode
-sys.dont_write_bytecode = True
-kwant_common = imp.load_source('kwant_common', 'kwant/_common.py')
-sys.dont_write_bytecode = _dont_write_bytecode_saved
-
 CONFIG_FILE = 'build.conf'
 README_FILE = 'README.rst'
 README_END_BEFORE = 'See also in this directory:'
-STATIC_VERSION_FILE = 'kwant/_static_version.py'
+STATIC_VERSION_PATH = ('kwant', '_kwant_version.py')
 REQUIRED_CYTHON_VERSION = (0, 22)
 NO_CYTHON_OPTION = '--no-cython'
-NO_GIT_OPTION = '--no-git'
 TUT_DIR = 'tutorial'
 TUT_GLOB = 'doc/source/tutorial/*.py'
 TUT_HIDDEN_PREFIX = '#HIDDEN'
 
+# Let Kwant itself determine its own version.  We cannot simply import kwant, as
+# it is not built yet.
+_dont_write_bytecode_saved = sys.dont_write_bytecode
+sys.dont_write_bytecode = True
+try:
+    imp.load_source(STATIC_VERSION_PATH[-1].split('.')[0],
+                    os.path.join(*STATIC_VERSION_PATH))
+except IOError:
+    pass
+_common = imp.load_source('_common', 'kwant/_common.py')
+sys.dont_write_bytecode = _dont_write_bytecode_saved
+
+version = _common.version
+version_is_from_git = _common.version_is_from_git
+
 try:
     import Cython
 except:
@@ -62,12 +71,6 @@ try:
 except ValueError:
     cythonize = True
 
-try:
-    sys.argv.remove(NO_GIT_OPTION)
-    use_git = False
-except ValueError:
-    use_git = True
-
 if cythonize and cython_version:
     from Cython.Distutils import build_ext
 else:
@@ -141,6 +144,10 @@ class build_tut(Command):
 class kwant_build(distutils_build):
     sub_commands = [('build_tut', None)] + distutils_build.sub_commands
 
+    def run(self):
+        distutils_build.run(self)
+        write_version(os.path.join(self.build_lib, *STATIC_VERSION_PATH))
+
 
 class test(Command):
     description = "build, then run the unit tests"
@@ -167,7 +174,7 @@ class test(Command):
 
 
 def git_lsfiles():
-    if not use_git:
+    if not version_is_from_git:
         return
 
     try:
@@ -213,7 +220,6 @@ class kwant_sdist(distutils_sdist):
                     if extension == 'pyx':
                         f.write(''.join([a, sep, stem, dot, 'c', '\n']))
                     f.write(name + '\n')
-                f.write(STATIC_VERSION_FILE + '\n')
                 f.write('MANIFEST\n')
 
         distutils_sdist.run(self)
@@ -232,42 +238,21 @@ with a comment).  It may well be incomplete.""",
                   banner(),
                   sep='\n', file=sys.stderr)
 
-def get_version_from_git():
-    if use_git:
-        return kwant_common.get_version_from_git()
+    def make_release_tree(self, base_dir, files):
+        distutils_sdist.make_release_tree(self, base_dir, files)
+        write_version(os.path.join(base_dir, *STATIC_VERSION_PATH))
 
 
-def read_static_version():
-    """Return the version as recorded inside the source code."""
+def write_version(fname):
+    # This could be a hard link, so try to delete it first.  Is there any way
+    # to do this atomically together with opening?
     try:
-        with open(STATIC_VERSION_FILE) as f:
-            contents = f.read()
-            assert contents[:11] == "version = '"
-            assert contents[-2:] == "'\n"
-            return contents[11:-2]
-    except:
-        return None
-
-
-def write_static_version(version):
-    """Record the version so that it is available without version control."""
-    with open(STATIC_VERSION_FILE, 'w') as f:
-        f.write("version = '%s'\n" % version)
-
-
-def version():
-    """Determine the version of Kwant.  Return it and save it in a file."""
-    git_version = get_version_from_git()
-    static_version = read_static_version()
-    if git_version is not None:
-        version = git_version
-        if static_version != git_version:
-            write_static_version(version)
-    elif static_version is not None:
-        version = static_version
-    else:
-        version = 'unknown'
-    return version
+        os.remove(fname)
+    except OSError:
+        pass
+    with open(fname, 'w') as f:
+        f.write("# This file has been created by setup.py.\n")
+        f.write("version = '{}'\n".format(version))
 
 
 def long_description():
@@ -463,7 +448,7 @@ def ext_modules(extensions):
 
 def main():
     setup(name='kwant',
-          version=version(),
+          version=version,
           author='C. W. Groth (CEA), M. Wimmer, '
                  'A. R. Akhmerov, X. Waintal (CEA), and others',
           author_email='authors@kwant-project.org',