This improves the implementation in gh-106643.
Previously, venv passed "(<prompt>) " to the activation scripts, but we want
to provide the original value so that users can inspect it in the
$VIRTUAL_ENV_PROMPT env var.
Note: Lib/venv/scripts/common/Activate.ps1 surrounded the prompt value with
parens a second time, so no change was necessary in that file.
Detect Cygwin and MSYS with `uname` instead of `$OSTYPE`
`$OSTYPE` is not defined by POSIX and may not be present in other shells.
`uname` is always available in any shell.
The `activate` script calls `hash -r` in two places to make sure the shell picks
up the environment changes the script makes. Before that, it checks to
see if the shell running the script is bash or zsh.
`hash -r` is specified by POSIX and is not exclusive to bash and zsh.
This guard prevents the script from calling `hash -r` in other
`#!/bin/sh`-compatible shells like dash.
When using python's built-in venv activaton script
warnings are printed when hashing is disabled in
bash or zsh, like;
`bash: hash: hashing disabled`
This output is not really useful to the end-user and has
been disabled in `virtualenv` for long.
This commit is based on:
28e85bcd80
Before, running deactivate from a bash shell configured to treat undefined variables as errors (`set -u`) would produce a warning:
```
$ python3 -m venv test
$ source test/bin/activate
(test) $ deactivate
-bash: $1: unbound variable
```
The activation scripts generated by venv were inconsistent in how they changed the shell's prompt. Some used `__VENV_PROMPT__` exclusively, some used `__VENV_PROMPT__` if it was set even though by default `__VENV_PROMPT__` is always set and the fallback matched the default, and one ignored `__VENV_PROMPT__` and used `__VENV_NAME__` instead (and even used a differing format to the default prompt). This change now has all activation scripts use `__VENV_PROMPT__` only and relies on the fact that venv sets that value by default.
The color of the customization is also now set in fish to the blue from the Python logo for as hex color support is built into that shell (much like PowerShell where the built-in green color is used).
