Problem: CLI buildout:extends not honored

Solution: check value explicitely and open corresponding files

news/592.bugfix

+Honor command-line buildout:extends

src/zc/buildout/buildout.py

@@ -387,6 +387,19 @@ class Buildout(DictMixin):
             )
             data = _update(data, cfg_data)
 
+        # extends from command-line
+        if 'buildout' in cloptions:
+            cl_extends = cloptions['buildout'].pop('extends', None)
+            if cl_extends:
+                for extends in cl_extends.value.split():
+                    download_options = for_download_options['buildout']
+                    cfg_data, _ = _open(
+                        os.path.dirname(extends),
+                        extends, [], download_options,
+                        override, set(), user_defaults
+                    )
+                    data = _update(data, cfg_data)
+
         # apply command-line options
         data = _update(data, cloptions)
 

src/zc/buildout/tests/buildout.txt

@@ -1895,6 +1895,49 @@ There are several things to note about this example:
 - Relative file names in extended options are interpreted relative to
   the directory containing the referencing configuration file.
 
+    >>> write(sample_buildout, 'buildout.cfg',
+    ... """
+    ... [buildout]
+    ... extends = b1.cfg
+    ...
+    ... [debug]
+    ... op = buildout
+    ... """)
+
+    >>> print_(system(buildout + ' buildout:extends="b2.cfg"'), end='')
+    Develop: '/sample-buildout/recipes'
+    Uninstalling debug.
+    Installing debug.
+    name base
+    op buildout
+    op1 b1 1
+    op2 b2 2
+    op3 b2 3
+    recipe recipes:debug
+
+    >>> print_(system(buildout + ' buildout:extends="b2.cfg %(b3)s"'
+    ... % dict(b3=os.path.join(other, 'b3.cfg'))), end='')
+    Develop: '/sample-buildout/recipes'
+    Uninstalling debug.
+    Installing debug.
+    name base
+    op buildout
+    op1 b1 1
+    op2 b2 2
+    op3 b2 3
+    op4 b3 4
+    op5 b3base 5
+    recipe recipes:debug
+
+    >>> write(sample_buildout, 'buildout.cfg',
+    ... """
+    ... [buildout]
+    ... extends = b1.cfg b2.cfg %(b3)s
+    ...
+    ... [debug]
+    ... op = buildout
+    ... """ % dict(b3=os.path.join(other, 'b3.cfg')))
+
 Loading Configuration from URLs
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