Update directions for macOS bash completion

docs/tasks/tools/install-kubectl.md

@@ -142,28 +142,29 @@ echo "source <(kubectl completion bash)" >> ~/.bashrc
 ```
 
 ### On macOS, using bash
-On macOS, autocompletion works if you install using `brew install kubectl`,
+On macOS, you will need to install bash-completion support via [Homebrew](https://brew.sh/) first:
-and not if you downloaded kubectl directly.
-
-Install the bash-completion support:
 
 ```shell
+## If running Bash 3.2 included with macOS
 brew install bash-completion
+## or, if running Bash 4.1+
+bash install bash-completion@2
 ```
 
-To add kubectl autocompletion to your current shell, run:
+Follow the "caveats" section of brew's output to add the appropriate bash completion path to your local .bashrc.
 
-```shell
+If you've installed kubectl using the [Homebrew instructions](#install-with-homebrew-on-macos) then kubectl completion should start working immediately.
-source $(brew --prefix)/etc/bash_completion
+
-source <(kubectl completion bash)
+If you have installed kubectl manually, then run: `source <(kubectl completion bash)`
-```
 
 To add kubectl autocompletion to your profile (so it is automatically loaded in future shells):
 
 ```shell
-echo "source $(brew --prefix)/etc/bash_completion" >> ~/.bash_profile
 echo "source <(kubectl completion bash)" >> ~/.bash_profile
 ```
+
+The Homebrew project is independent from kubernetes, so the bash-completion packages are not guaranteed to work.
+
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