gnu-utils: add README, simplify plugin

plugins/gnu-utils/README.md

+# gnu-utils plugin
+
+This plugin binds GNU coreutils to their default names, so that you don't have
+to call them using their prefixed name, which starts with `g`. This is useful
+in systems which don't have GNU coreutils installed by default, mainly macOS
+or FreeBSD, which use BSD coreutils.
+
+To use it, add `gnu-utils` to the plugins array in your zshrc file:
+```zsh
+plugins=(... gnu-utils)
+```
+
+The plugin works by changing the path that the command hash points to, so
+instead of `ls` pointing to `/bin/ls`, it points to wherever `gls` is
+installed.
+
+Since `hash -rf` or `rehash` refreshes the command hashes, it also wraps
+`hash` and `rehash` so that the coreutils binding is always done again
+after calling these two commands.
+
+Look at the source code of the plugin to see which GNU coreutils are tried
+to rebind. Open an issue if there are some missing.
+
+## Other methods
+
+The plugin also documents two other ways to do this:
+
+1. Using a function wrapper, such that, for example, there exists a function
+named `ls` which calls `gls` instead. Since functions have a higher preference
+than commands, this ends up calling the GNU coreutil. It has also a higher
+preference over shell builtins (`gecho` is called instead of the builtin `echo`).
+
+2. Using an alias. This has an even higher preference than functions, but they
+could be overridden because of a user setting.
+
+## Author
+
+- [Sorin Ionescu](https://github.com/sorin-ionescu).

plugins/gnu-utils/gnu-utils.plugin.zsh

@@ -5,9 +5,12 @@
 #       VERSION:  1.0.0
 # ------------------------------------------------------------------------------
 
+# Detect if GNU coreutils are installed by looking for gwhoami
+if [[ ! -x "${commands[gwhoami]}" ]]; then
+  return
+fi
 
-if [[ -x "${commands[gwhoami]}" ]]; then 
-  __gnu_utils() {
+__gnu_utils() {
   emulate -L zsh
   local gcmds
   local gcmd
@@ -36,48 +39,45 @@ if [[ -x "${commands[gwhoami]}" ]]; then
   gcmds+=('gsed' 'gtar' 'gtime')
 
   for gcmd in "${gcmds[@]}"; do
-      #
+    # Do nothing if the command isn't found
+    (( ${+commands[$gcmd]} )) || continue
+    
     # This method allows for builtin commands to be primary but it's
     # lost if hash -r or rehash -f is executed. Thus, those two 
     # functions have to be wrapped.
     #
-      (( ${+commands[$gcmd]} )) && hash ${gcmd[2,-1]}=${commands[$gcmd]}
+    hash ${gcmd[2,-1]}=${commands[$gcmd]}
 
-      #
     # This method generates wrapper functions.
     # It will override shell builtins.
     #
-      # (( ${+commands[$gcmd]} )) && \
     # eval "function $gcmd[2,-1]() { \"${prefix}/${gcmd//"["/"\\["}\" \"\$@\"; }"
 
-      #
     # This method is inflexible since the aliases are at risk of being
     # overridden resulting in the BSD coreutils being called.
     #
-      # (( ${+commands[$gcmd]} )) && \
     # alias "$gcmd[2,-1]"="${prefix}/${gcmd//"["/"\\["}"
   done
 
   return 0
-  }
-  __gnu_utils;
+}
+__gnu_utils
 
-  function hash() {
+function hash() {
   if [[ "$*" =~ "-(r|f)" ]]; then
     builtin hash "$@"
     __gnu_utils
   else
     builtin hash "$@"
   fi
-  }
+}
 
-  function rehash() {
+function rehash() {
   if [[ "$*" =~ "-f" ]]; then
     builtin rehash "$@"
     __gnu_utils
   else
     builtin rehash "$@"
   fi
-  }
-fi
+}