[readme] include deeper integration instructions for fish

README.md

@@ -31,6 +31,8 @@
       - [Automatically call `nvm use`](#automatically-call-nvm-use)
     - [zsh](#zsh)
       - [Calling `nvm use` automatically in a directory with a `.nvmrc` file](#calling-nvm-use-automatically-in-a-directory-with-a-nvmrc-file)
+    - [fish](#fish)
+      - [Calling `nvm use` automatically in a directory with a `.nvmrc` file](#calling-nvm-use-automatically-in-a-directory-with-a-nvmrc-file-1)
 - [License](#license)
 - [Running Tests](#running-tests)
 - [Bash Completion](#bash-completion)
@@ -536,6 +538,45 @@ add-zsh-hook chpwd load-nvmrc
 load-nvmrc
 ```
 
+#### fish
+
+##### Calling `nvm use` automatically in a directory with a `.nvmrc` file
+This requires that you have [bass](https://github.com/edc/bass) installed.
+```fish
+# ~/.config/fish/functions/nvm.fish
+function nvm
+  bass source ~/.nvm/nvm.sh --no-use ';' nvm $argv
+end
+
+# ~/.config/fish/functions/nvm_find_nvmrc.fish
+function nvm_find_nvmrc
+  bass source ~/.nvm/nvm.sh --no-use ';' nvm_find_nvmrc
+end
+
+# ~/.config/fish/functions/load_nvm.fish
+function load_nvm --on-variable="PWD"
+  set -l default_node_version (nvm version default)
+  set -l node_version (nvm version)
+  set -l nvmrc_path (nvm_find_nvmrc)
+  if test -n "$nvmrc_path"
+    set -l nvmrc_node_version (nvm version (cat $nvmrc_path))
+    if test "$nvmrc_node_version" = "N/A"
+      nvm install $nvmrc_node_version
+    else if test nvmrc_node_version != node_version
+      nvm use $nvmrc_node_version
+    end
+  else if test "$node_version" != "$default_node_version"
+    echo "Reverting to default Node version"
+    nvm use default
+  end
+end
+
+# ~/.config/fish/config.fish
+# You must call it on initialization or listening to directory switching won't work
+load_nvm
+```
+
+
 ## License
 
 nvm is released under the MIT license.