mv: prompts to overwrite read-only file when stdin is not a terminal

When mv tries to overwrite a file with mode 0555 (read-only), it prompts for confirmation even when stdin is not a terminal. GNU mv silently proceeds in this scenario.

This is the mv equivalent of #7326, which was fixed for rm in PR #7492.

Expected behavior (GNU coreutils)

$ touch target && chmod 555 target
$ echo content > source
$ mv source target < /dev/null
$ # No promprt, file is moved
$ cat target

Actual behavior (uutils)

$ touch target && chmod 555 target
$ echo content > source
$ mv source target < /dev/null
mv: replace 'target', overriding mode 0555 (r-xr-xr-x)?
$ # Prompts and waits/fails, file is NOT moved

Reproducing script

#!/usr/bin/env bash
set -e

WORKDIR=$(mktemp -d)
cd "$WORKDIR"
trap "rm -rf $WORKDIR" EXIT

# Create a read-only target file
echo "original" > target
chmod 555 target

# Create source file
echo "replacement" > source

echo "=== Testing mv with stdin redirected from /dev/null ==="
echo "Running: mv source target < /dev/null"

# This should NOT prompt when stdin is not a terminal
if timeout 2 mv source target < /dev/null 2>&1; then
    echo "PASS: mv completed without prompting"
    echo "target contents: $(cat target)"
else
    echo "FAIL: mv prompted or timed out (exit code: $?)"
    echo "GNU mv would silently overwrite the file"
fi

Start at the mv command entry point and reproduce the issue with the supplied shell script, using a mode-0555 target and stdin redirected from /dev/null. Review the related rm issue #7326 and fix in PR #7492 for relevant behavior. Done means mv completes without prompting, moves source over target, and leaves the replacement content in target.