bug#14013: 24.3.50; dired-isearch-filenames-regexp is matching text outside filenames

[Juri Linkov <juri@jurta.org>]

> This works surprisingly well.  Maybe there are more corner cases,
> but something already works with quick tests:

But there is a long-standing bug in query-replace.
The optimization that uses `match-again` and `looking-at`
ignores search-related variables such as
isearch-search-fun-function, replace-re-search-function, etc.

Here's is a test case that demonstrates the problem in current master
with the recent addition of dired-isearch-search-filenames:

1. cd /tmp; touch file1; ln -s file1 file2
2. enter Wdired and move point to the beginning of file2
3. C-M-% .* RET foo RET
4. answer `n` when asked to replace `file2`

After that the remaining part of the same line is highlighted,
i.e. the part after "file2" (that is a symbolic link) in:

  file2 -> file1

This is because the `match-again` optimization uses `(looking-at ".*")`
after the previous replacement "file2" to ask about the next replacement
of " -> file1" that ignores isearch-search-fun-function.

I believe it would be safe to just remove this `match-again` optimization
from `perform-replace`.