various docs updates (#29018)

* website/docs: add sensitivity warning to output documentation

fixes #28005

* website/docs: add note about ** to fileset documentation

closes #24220

* website/docs: add note that `dynamic` expressions aren't included in json config output

closes #28346

* website: the provider installer isn't necessarily concurrency safe

closes #28367

website/docs/cli/commands/output.html.md

@@ -33,6 +33,10 @@ The command-line flags are all optional. The list of available flags are:
 * `-state=path` - Path to the state file. Defaults to "terraform.tfstate".
     Ignored when [remote state](/docs/language/state/remote.html) is used.
 
+-> **Note:** When using the `-json` or `-raw` command-line flag, any sensitive
+values in Terraform state will be displayed in plain text. For more information,
+see [Sensitive Data in State](/docs/language/state/sensitive-data.html).
+
 ## Examples
 
 These examples assume the following Terraform output snippet.

website/docs/cli/config/config-file.html.md

@@ -358,6 +358,10 @@ Terraform will never itself delete a plugin from the plugin cache once it has
 been placed there. Over time, as plugins are upgraded, the cache directory may
 grow to contain several unused versions which you must delete manually.
 
+-> **Note:** The plugin cache directory is not guaranteed to be concurrency
+safe. The provider installer's behavior in environments with multiple `terraform
+init` calls is undefined. 
+
 ### Development Overrides for Provider Developers
 
 -> **Note:** Development overrides work only in Terraform v0.14 and later.

website/docs/internals/json-format.html.md

@@ -451,6 +451,8 @@ Each unevaluated expression in the configuration is represented with an `<expres
 }
 ```
 
+-> **Note:** Expressions in `dynamic` blocks are not included in the configuration representation.
+
 ### Block Expressions Representation
 
 In some cases, it is the entire content of a block (possibly after certain special arguments have already been handled and removed) that must be represented. For that, we have an `<block-expressions-representation>` structure:

website/docs/language/functions/fileset.html.md

@@ -26,6 +26,10 @@ Supported pattern matches:
 - `[CLASS]` - matches any single non-separator character inside a class of characters (see below)
 - `[^CLASS]` - matches any single non-separator character outside a class of characters (see below)
 
+Note that the doublestar (`**`) must appear as a path component by itself. A
+pattern such as /path** is invalid and will be treated the same as /path*, but
+/path*/** should achieve the desired result.
+
 Character classes support the following:
 
 - `[abc]` - matches any single character within the set