TYPO3 Core

file typo3/sysext/extbase/ext_typoscript_setup.txt
contains link to old project on wiki:

 # if enabled, default controller and/or action is skipped when creating URIs through the URI Builder (see http://forge.typo3.org/projects/typo3v4-mvc/wiki/Skip_default_arguments_in_URIs)
  96                 skipDefaultArguments = 0

this page is not accessible any more.

Internet archvive helped me recover following text:

Skip default arguments in URIs
This feature is part of Extbase 1.4, that will be included in TYPO3 4.6

From version 1.4 on you can configure Extbase to skip the URI arguments for controller and action if they are equal to the respective default in the target plugin.

NOTE: This only works reliably, if you do not modify the default controller / actions of a plugin via FlexForms!

You can enable the feature with following TypoScript configuration:

plugin.tx_yourextension {
    features {
        skipDefaultArguments = 1
    }
}
You can enable the feature globally, but make sure that all installed Extbase extensions are compatible with that setting:

config.tx_extbase {
    features {
        skipDefaultArguments = 1
    }
}

We should move this documentation to a proper place and fix the link.