A better UI than perform-replace (was: Rename refactoring, or something like that)

[Oleh Krehel <ohwoeowho@gmail.com>]

Dmitry Gutov <dgutov@yandex.ru> writes:

> 5. Feel hugely motivated, and write a better UI for all of that.

I think a better UI for `perform-replace' is warranted.  The current
thing is very basic:

- No good way to see how many matches there are.
- No good way to get an overview of matches per buffer.
- No good way to pause the replacement procedure.
- No good way to undo a replacement.

An idea to improve this would be with a permanent *replace* buffer,
similar to `dired' or *Buffer List*. This buffer would be visible during
the replacement operation, together with the actual buffers that contain
the candidates. Here are some ideas for key bindings and the general
interface:

0. The *replace* buffer would be organized in branches by buffer, just
like *xref* is currently.

1. "y" would mark the current item for replacement, which corresponds to
the current line in the *replace* buffer, and advance to the next line.

2. "n" would mark the current item for non-replacement, and advance to
the next line. This is to distinguish the items for which no decision
was made yet: they don't have a `y' or `n' mark.

3. "Y" would mark all items from the current one until the end of the
current buffer branch. "N" would work in a similar way.

4. "c" could change the replacement text for a single item. The mark
would change appropriately.

5. "C" could change the replacement text for all following items.

6. "x" would execute all requested changes. 

7. "e" would launch an `ediff' session to review the changes that "x"
would do.

8. After "x", the *replace* buffer stays behind until the user kills it.
It should serve to review the changes. Possibly "u" could be used to
revert a performed change for the current item.

9. "C-n", "C-p" and any other navigational commands should work as
usual. Except changing the current item in *replace* should result in
that item being displayed in its native buffer - exactly what "C-o"
currently does in *xref*.

To re-describe things in a shorter way, *replace* should be a staging
area for the `perform-replace' operation. With the ability to quickly
view and manipulate the separate replacements, the ability to defer it
indefinitely, and the ability to finalize the operation with "x".

I post this idea here for feedback. Maybe there's a better way to do
this. Maybe there are ideas to further improve my *replace* proposal.
Maybe there's a wish to have this functionality in the core.  Maybe
someone even wants to implement it right away (I can do it eventually,
if there are no volunteers). Let me know.

    Oleh