Use of tee(2) to speedup reading from pipes

Hi,

bash currently probes a pipe w/ lseek, sees it isn't seekable, and then
falls back to reading 1 byte at a time.

A few years ago, dash adopted [0] use of tee(2) to peek at the contents
of stdin and read the amount of bytes left instead rather than 1.

Could this be considered for bash too? My interest in this is partly
speed but also to avoid a lot of noisy read()s of size 1 which can
obfuscate actual problems and can be hard to decipher (as you have to
concatenate the values from each line mentally).

[0] 44b15ea09a9ee5872cf477e4ffc6b42ef37d1e46 with some followups
    afterwards in 1713d1d6592f09f23b5abfb4562cbe5a7615fb1a,
    41457be81fa7b45af9d9ca402454fee0e555620f,
    and 0679594e72403f4a6d7890e627b75816f6feb0d5.

thanks,
sam

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