bug#32668: 26.1; Give find-dired prefix argument behaviour equivalent to that of rgrep

[Phil Sainty]

In bug#27456 "Not possible to use -prune with find-dired", workarounds
were provided for the issue that, due to the way that `find-dired'
constructs its find command, some common usage patterns for the `find'
command can't be used with `find-dired'.

I think it would be useful and consistent for `find-dired' to acquire
the prefix argument behaviour of `rgrep', which does the following:

> With C-u prefix, you can edit the constructed shell command line
> before it is executed.
> With two C-u prefixes, directly edit and run [the find command].

Giving the user access to edit the final command before it is executed
would allow users to massage otherwise-unusable syntax into a working
command.

This would give users an alternative solution to the kind of problem
presented in the aforementioned bug report, and would be especially
useful for those who are unfamiliar with the particular find options
needed to work around the problem at present.






In GNU Emacs 26.1 (build 1, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll
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 of 2018-06-19 built on shodan
Windowing system distributor 'The X.Org Foundation', version 11.0.11906000
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