cd completion gives `dir` and `dir/` when CDPATH is set

[jmou]

Describe the bug

This bug seems to require a few things to occur:

• CDPATH must be set
• The parameter being completed must be the full name of a directory in the current directory
• No other directory is a valid completion

To reproduce

$ CDPATH=.
$ cd /
$ cd usr[TAB][TAB]
usr/  usr// 

Expected behavior

Should have completed to cd bin/

Versions (please complete the following information)

• Operating system name/distribution and version: Fedora 43
• bash version, echo "$BASH_VERSION": 5.3.0(1)-release
• bash-completion version, (IFS=.; echo "${BASH_COMPLETION_VERSINFO[*]}"): git commit ed0ae10 and later

Additional context

This bug is in git but not in the distribution package. It appears to be a regression from commit ed0ae10 (the bug does not occur in its parent).

Commenting out this section appears to make the issue go away (although I don't understand what it is for):

    if ((${#_cdpaths[@]} == 1)); then
        _p=${_cdpaths[0]}
        if [[ $_p == "$cur" && $_p != */ ]]; then
            _cdpaths[0]=$_p/
        fi
    fi

Debug trace

[TechWizard9999]

@scop
Can I work on this issue?