Section on stricter env rules

Author: sholderbach

blog/2024-04-30-nushell_0_93_0.md

@@ -29,6 +29,7 @@ As part of this release, we also publish a set of optional plugins you can insta
     - [*Hall of fame*](#hall-of-fame-toc)
         - [*Bug fixes*](#bug-fixes-toc)
         - [*Enhancing the documentation*](#enhancing-the-documentation-toc)
+        - [*Stricter rules around setting environment variables*](#stricter-rules-around-setting-environment-variables-toc)
     - [*Our set of commands is evolving*](#our-set-of-commands-is-evolving-toc)
         - [*New commands*](#new-commands-toc)
         - [*Changes to existing commands*](#changes-to-existing-commands-toc)
@@ -92,6 +93,35 @@ Thanks to all the contributors below for helping us making the documentation of
 | ------------------------------------ | ----------- | ------------------------------------------------------- |
 | [@author](https://github.com/author) | ...         | [#12345](https://github.com/nushell/nushell/pull/12345) |
 
+## Stricter rules around setting environment variables [[toc](#table-of-content)]
+
+::: warning Breaking change
+See a full overview of the [breaking changes](#breaking-changes-toc)
+:::
+
+The setting of environment variables via the following ways:
+- `$env.VAR_NAME = ...` assignment
+- scopes with the `with-env` command
+- the short hand syntax `FOO=bar command-to-run` 
+- the `load-env` command
+
+will now consistently prohibit you from changing a set of special environment variables controlled by Nushell.
+Currently this is the following set (already valid for `$env.` assignment):
+- `$env.PWD`
+- `$env.FILE_PWD`
+- `$env.CURRENT_FILE`
+This set may be expanded by future breaking changes to ensure consistent semantics of those special variables
+
+Furthermore the `FOO=bar BAZ=bla command` shorthand syntax to set an environment variable for the scope of one command is now stricter.
+It will disallow you from repeating the same environment variable name twice and instead return an error ([#12523](https://github.com/nushell/nushell/pull/12523)).
+
+```nushell
+# Now raises an error
+FOO=bar FOO=bla command
+```
+
+Additionally, we standardize on using records to pass a map of environment variables to the `with-env` command, and thus [deprecate the other previously allowed forms with this release](#with-env-toc).
+
 ## Our set of commands is evolving [[toc](#table-of-content)]
 
 ### New commands [[toc](#table-of-content)]