Add new fmt plugins for build file formatting

docs/markdown/Releases/upgrade-tips.md

@@ -24,7 +24,7 @@ You do not need to land every upgrade into your organization—often, you will w
 First, see if Pants can automatically fix any safe deprecations for you:
 
 ```bash
-# You may want to use `--no-fmt` if your BUILD files are already formatted.
+# To avoid unrelated formatting changes, you may want to use `--no-fmt`.
 ❯ ./pants update-build-files --no-fmt ::
 ```
 

docs/markdown/Using Pants/concepts/targets.md

@@ -43,9 +43,7 @@ Each target type has different _fields_, or individual metadata values. Run `./p
 
 All target types have a `name` field, which is used to identify the target. Target names must be unique within a directory.
 
-Use [`./pants tailor ::`](doc:initial-configuration#5-generate-build-files) to automate generating BUILD files.
-You can autoformat build files by opting into one of the plugins under `pants.backend.build_files.fmt` and
-running `./pants fmt **/BUILD` or `./pants fmt ::` (which formats everything).
+You can autoformat `BUILD` files by enabling a `BUILD` file formatter by adding it to `[GLOBAL].backend_packages` in `pants.toml` (such as `pants.backend.build_files.fmt.black` [or others](https://www.pantsbuild.org/v2.13/docs/enabling-backends)). Then to format, run `./pants fmt '**/BUILD'` or `./pants fmt ::` (formats everything).
 
 Target addresses
 ================

pants.toml

@@ -110,6 +110,10 @@ ignore_adding_targets = [
   "src/python/pants/backend/terraform:hcl2_parser0",
 ]
 
+[update-build-files]
+# We use `pants.backend.build_files.fmt.black`
+fmt = false
+
 [pex]
 venv_use_symlinks = true