From: Chandra Pratap <chandrapratap3519@gmail.com>

Among Git's environment variable, the ones marked as "Boolean"
accept values in a way similar to Boolean configuration variables,
i.e. values like 'yes', 'on', 'true' and positive numbers are
taken as "on" and values like 'no', 'off', 'false' are taken as
"off".
GIT_FLUSH can be used to force Git to use non-buffered I/O when
writing to stdout. It can only accept two values, '1' which causes
Git to flush more often and '0' which makes all output buffered.
Make GIT_FLUSH accept more values besides '0' and '1' by turning it
into a Boolean environment variable, modifying the required logic.
Update the related documentation.

Signed-off-by: Chandra Pratap <chandrapratap3519@gmail.com>

Submitted-As: https://lore.kernel.org/git/pull.1628.v2.git.1704268708720.gitgitgadget@gmail.com
In-Reply-To: https://lore.kernel.org/git/pull.1628.git.1703955246308.gitgitgadget@gmail.com