Hide summary file actions when a selected file does not match

[danxuliu]

When several files are selected and one of them can not be deleted the Delete file action is not shown in the summary. This pull request extends that behaviour too to the other file actions in the summary (Move or copy and Download), so now an action is shown in the summary only if it can be executed on all the currently selected files.

This is a requisite for proper handling of encrypted folders in #6670.

Hiding the actions may not be the best solution regarding the user experience, as a user may not understand why the actions do not appear if she selects all the files in a folder, or she may expect the actions to always be available and to be performed only on the matching files.

In the future it may be worth considering an alternative approach, like a notification letting the user know on which files the action was not executed, or a dialog informing about that before performing the action, or a visible but disabled action that hints on why it is disabled, or whatever (there are probably much better solutions, those are just examples ;-) ).

But for the time being I am afraid that we will have to live with hidden actions ;-)

[codecov]

Codecov Report

Merging #7046 into master will not change coverage.
The diff coverage is n/a.

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##             master    #7046   +/-   ##
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  Coverage     50.62%   50.62%           
  Complexity    24290    24290           
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  Files          1577     1577           
  Lines         92890    92890           
  Branches       1358     1358           
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  Hits          47028    47028           
  Misses        45862    45862