History search: wrong pos. after `Bksp` over typo

[Michael Allan]

Configuration Information [Automatically generated]:
Machine: x86_64
OS: linux-gnu
Compiler: x86_64-pc-linux-gnu-gcc
Compilation CFLAGS: -march=native -O2 -pipe -Wno-parentheses 
-Wno-format-security
uname output: Linux primeval 5.4.30-gentoo #33 SMP Wed Jul 29 00:03:46 EDT 2020 
x86_64 AMD Ryzen 7 3700X 8-Core Processor AuthenticAMD GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 5.0
Patch Level: 17
Release Status: release

Description:
    During history search, Bash allows one to correct the search term
    by backspacing, e.g. after making a typo, but it fails to correct
    the search position in response.

    A typo is like a ‘wrong turn at Albuquerque’, it can get one lost.
    Backspacing and erasing part of the search term *should* take one
    back to Albuquerque, but does not; while it corrects the search
    term, it fails to correct the search position (inconsistency)
    which leaves one lost.

Repeat-By:
    During a history search, I make a typo while entering the search
        term (wrong term!).  Bash either finds a match for my typo, or it
        beeps at me.  In either case, the search position has now changed,
        leaving me somewhere in the middle of history (wrong place!).

    I backspace to undo my typo.  This undoes the typo, but (here is
        the bug) does not undo the change to the search position.  Still I
        am at the wrong place.  As I retype the search term (correctly
        this time), the results are not what I expect.  I remain lost in
        Bash history.

    I could find no satisfactory workarounds.  See e.g.
    https://unix.stackexchange.com/q/523543.

Fix:
    I think the following might work. It seems to be how Emacs works
    during interactive text searches.

        As the user backspaces stepwise over a search term, reverting at
    each step to a previous value, revert the search position to *its*
    correponding, previous value.

-- 
Michael Allan

Toronto, +1 416 699 9528
http://reluk.ca/