bash: fix PS1=abc bash

[john-peterson]

if the shell already has a name don't change it. this is the same behaviour as bash itself

env -u PS1 bash --noprofile --norc
echo $PS1
\s-\v$

PS1=abc bash --noprofile --norc
echo $PS1
abc

[TomJo2000]

I'm not quite sure what perceived bug you are attempting to fix in this PR.

PS1 is not the name of the shell.
It's the shell prompt.

\s-\v$ is the expected default if no other value is set in the profile ($PREFIX/etc/profile), system bashrc file ($PREFIX/etc/bash.bashrc) or user .bashrc file (~/.bashrc).

The relevant section from man 1 bash¹ reads:

PS1    The value of this parameter is expanded (see PROMPTING below)
       and used as the primary prompt string.  The default value is
       ``\s-\v\$ ''.

This default \s-\v\$ is evaluates to²: bash-5.2$
While our default assignment of \[\e[0;32m\]\w\[\e[0m\] \[\e[0;97m\]\$\[\e[0m\] evaluates to² ~ $ ,
with the path in green (and truncated to 2 segments by the PROMPT_DIRTRIM=2 above), and the $ in white.

It is probably worthwhile to allow users to set a PS1 by passing it along to a spawned bash shell,
though this isn't a usecase I have ever encountered before.

Footnotes

1. https://man.archlinux.org/man/bash.1#PS1 ↩

2. https://man.archlinux.org/man/bash.1#PROMPTING ↩ ↩²

[TomJo2000]

Consider using [[ -v PS1 ]]¹ instead to avoid the dependency on grep.

Suggested change

	PS1='\[\e[0;32m\]\w\[\e[0m\] \[\e[0;97m\]\$\[\e[0m\] '
	# Allow users to override $PS1 by passing it to the invocation of bash as an environment variable
	[[ -v PS1 ]] || PS1='\[\e[0;32m\]\w\[\e[0m\] \[\e[0;97m\]\$\[\e[0m\] '

Footnotes

1. https://man.archlinux.org/man/bash.1#CONDITIONAL_EXPRESSIONS:~:text=set%20builtin%20below.-,%2Dv%20varname,-True%20if%20the ↩

[TomJo2000]

termux-packages/packages/bash/build.sh

Lines 1 to 7 in 507c890

	TERMUX_PKG_HOMEPAGE=https://www.gnu.org/software/bash/
	TERMUX_PKG_DESCRIPTION="A sh-compatible shell that incorporates useful features from the Korn shell (ksh) and C shell (csh)"
	TERMUX_PKG_LICENSE="GPL-3.0"
	TERMUX_PKG_MAINTAINER="Joshua Kahn @TomJo2000"
	_MAIN_VERSION=5.2
	_PATCH_VERSION=37
	TERMUX_PKG_VERSION=${_MAIN_VERSION}.${_PATCH_VERSION}

By the way you'll need to add TERMUX_PKG_REVISION=1 to the bash build.sh.
Preferably under the package version.

Since this is an update to part of the package it should be recognized by the package manager as such.