chore: Add installation instructions for zsh

Author: Oliver Weiler

README.md

@@ -29,15 +29,33 @@ Add the following line to your `.bashrc` (Linux) or `.bash_profile` (macOS) to i
 . "$HOME/.up/up"
 ```
 
-Add the following line to your `.bashrc` (Linux) or `.bash_profile` (macOS) to enable `up`'s Bash completion.
+Add the following line to your `.bashrc` (Linux) or `.bash_profile` (macOS) to enable `up`'s shell completion.
 
 ```sh
 . "$HOME/.up/completion/bash/up"
 ```
 
 ### git & zsh
 
-TBD
+Clone `up`'s git repository.
+
+```sh
+git clone https://github.com/helpermethod/up ~/.up
+```
+
+Add the following line to your `.zshrc` to install `up`.
+
+```
+. "$HOME/.up/up"
+```
+
+Add the following lines to your `.zshrc` to enable `up`'s shell completion.
+
+```sh
+autoload -U +X compinit && compinit
+autoload -U +X bashcompinit && bashcompinit
+. "$HOME/.up/completion/bash/up"
+```
 
 ## Usage
 

completion/bash/up

@@ -5,7 +5,9 @@ _up() {
 	local -r pwd_without_leading_slash=${PWD:1}
 
 	local basenames=()
-	IFS=/ read -r -a basenames <<<"${pwd_without_leading_slash%/*}"
+        while IFS= read -r -d/; do
+          basenames+=("$REPLY")
+        done <<<"$pwd_without_leading_slash"
 
 	[[ $PWD != / ]] && basenames+=(/)