[Issue 21059] install.sh: posix_terminal returns false on Linux Mint 20

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21059

Dlang Bot <dlang-bot at dlang.rocks> changed:

           What    |Removed                     |Added
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           Keywords|                            |pull

--- Comment #3 from Dlang Bot <dlang-bot at dlang.rocks> ---
@veelo created dlang/installer pull request #463 "Fixes issue 21059: installer
fails when piped on Posix." fixing this issue:

- Fixes issue 21059.

  The assumption that $SHLVL increases when the script is run does not always
hold. $SHLVL does not increase if the script is piped into bash, thereby
failing to detect Posix. If the default terminal shell is not bash, $SHLVL
might also be 1 on Posix.

https://github.com/dlang/installer/pull/463

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