Remove superflous action summaries from command output

These consume a lot of space, and are often not helpful given the simple
usage patterns that dominate the handbook.

This change removes any action summary that does not contain notneeded.
The exception is useful, because by default notneeded results are not
renderer individually.

Ping #1009
Ping #1048

docs/conf.py

@@ -63,6 +63,9 @@
     # should still be functional and save 30+% of line length
     (r'(?P<lead>[0-9a-f]{8})[0-9a-f]{32}', r'\g<lead>✂SHA1'),
     (r'(?P<lead>[0-9a-f]{8})[0-9a-f]{24}', r'\g<lead>✂MD5'),
+    # remove any action summary that contains no `notneeded`, the latter
+    # need to be kept, because they are not renderer individually
+    (r'(action summary:(\n^  \S+ \(\S+(?<!notneeded): \d+\)$)+)\n(?!  )', ''),
 ]
 # pre-crafted artificial environment to run the code examples in
 # start with all datalad settings