Add basic bash completion

Signed-off-by: Ahmet Alp Balkan <ahmetb@google.com>

README.md

@@ -31,11 +31,11 @@ Context "dublin" set.
 Aliased "gke_ahmetb_europe-west1-b_dublin" as "dublin".
 ```
 
-## Help wanted
+[**Set up `bash` completion →**](completion/README.md)
 
-- [ ] bash completion
-- [ ] zsh completion
-- [ ] homebrew formula/tap
+### Help wanted
+
+[ ] homebrew formula/tap
 
 -----
 

completion/README.md

@@ -0,0 +1,19 @@
+kubectx provides shell completion scripts to complete context names, making it
+even faster to switch between contexts easily.
+
+## Bash setup
+
+Copy the `kubectx.bash` file to your HOME directory:
+
+    cp kubectx.bash ~/.kubectx.bash
+
+And source it in your `~/.bashrc` file by adding the line:
+
+    [ -f ~/.kubectx.bash ] && source ~/.kubectx.bash
+
+Start a new shell, type `kubectx`, then hit <kbd>Tab</kbd> to see the existing
+contexts.
+
+You can Add `TAB: menu-complete` to your `~/.inputrc` to cycle through the
+options with <kbd>Tab</kbd>.
+

completion/kubectx.bash

@@ -0,0 +1,8 @@
+_kube_contexts()
+{
+  local curr_arg;
+  curr_arg=${COMP_WORDS[COMP_CWORD]}
+  COMPREPLY=( $(compgen -W "- $(kubectl config get-contexts | awk '{print $2}' | tail -n +2)" -- $curr_arg ) );
+}
+
+complete -F _kube_contexts kubectx