misc: generate a version number that's compatible with PEP 440 (#25596)

setup.py

@@ -27,19 +27,29 @@ class eo_sdist(sdist):
             os.remove('VERSION')
 
 def get_version():
+    '''Use the VERSION, if absent generates a version with git describe, if not
+       tag exists, take 0.0- and add the length of the commit log.
+    '''
     if os.path.exists('VERSION'):
-        version_file = open('VERSION', 'r')
-        version = version_file.read()
-        version_file.close()
-        return version
+        with open('VERSION', 'r') as v:
+            return v.read()
     if os.path.exists('.git'):
-        p = subprocess.Popen(['git', 'describe', '--dirty', '--match=v*'], stdout=subprocess.PIPE)
+        p = subprocess.Popen(['git','describe','--dirty=.dirty','--match=v*'],
+                stdout=subprocess.PIPE, stderr=subprocess.PIPE)
         result = p.communicate()[0]
         if p.returncode == 0:
-            version = str(result.split()[0][1:])
-            version = version.replace('-', '.')
+            result = result.decode('ascii').strip()[1:] # strip spaces/newlines and initial v
+            if '-' in result: # not a tagged version
+                real_number, commit_count, commit_hash = result.split('-', 2)
+                version = '%s.post%s+%s' % (real_number, commit_count, commit_hash)
+            else:
+                version = result
             return version
-    return '0'
+        else:
+            return '0.0.post%s' % len(
+                    subprocess.check_output(
+                            ['git', 'rev-list', 'HEAD']).splitlines())
+    return '0.0'
 
 def data_tree(destdir, sourcedir):
     extensions = ['.css', '.png', '.jpeg', '.jpg', '.gif', '.xml', '.html', '.js']