Add autoenv, automatic environment setup

Using a hook, automatically detect when `.enter` and `.exit` scripts
and source them when changing the shells current directory.

autoenv/autoenv.plugin.zsh

@@ -1,7 +1,9 @@
 # Automatically update the environment when the current working directory
 # changes, this is a reimplementation of the ideas found in the repository
-# https://github.com/Tarrasch/zsh-autoenv stripped down to suit my specific
-# needs.
+# https://github.com/Tarrasch/zsh-autoenv stripped down to bare essentials.
+#
+# The secret sauce can be found at the bottom of this file, where the `chpwd`
+# hook function `_autoenv_chpwd` is added.
 
 # Global entered directories array.
 _autoenv_entered=()
@@ -9,18 +11,19 @@ _autoenv_entered=()
 # Check if the given file is authorized, if not prompt the user to authorize,
 # ignore, or view the file. Authorized files and their modified times are
 # stored in the ~/.cache/autoenv/authorized file to make authorization
-# persistant.
+# persistent.
 _autoenv_authorized() {
   local file=$1
   # If autoenv cache directory does not exist, create it.
-  local cache_dir=~/.config/autoenv
+  local cache_dir=~/.cache/autoenv
   ! [ -d $cache_dir ] && mkdir -p $cache_dir
   local authorized_file=$cache_dir/authorized
-  # Define the associative array to hold authorized key value pairs.
-  # If the authorized file exists, load it into an associative array.
+  # Define a map to hold authorized key value pairs.
   typeset -A authorized=()
+  # If the authorized file exists, load it into the map.
   [ -f $authorized_file ] && typeset -A authorized=(`cat $authorized_file`)
-  # If the given file has been authorized, return.
+  # If the given file has been authorized, i.e. the modified time matches that
+  # held in the authorized file, return.
   local modified_time=`zstat +mtime $file`
   [ "$authorized[$file]" = "$modified_time" ] && return
   # Prompt to authorize file.
@@ -65,18 +68,18 @@ _autoenv_exit() {
 
 # Find a directory containing a .enter file by searching up the directory tree
 # starting in the current directory.
-_autoenv_find_enter() {
+_autoenv_find_enter_directories() {
   local current=$PWD
   # If an enter script is found in the current directory, return it.
-  [ -f "$current/.enter" ] && echo $current
+  [ -f $current/.enter ] && echo $current
   # Loop until an enter script or the root directory is found.
   while true; do
     # Go up one directory and make the path absolute.
     local next=$current/..; local next=${next:A}
+    # If an enter script is found in the current directory, return it.
+    [ -f $next/.enter ] && echo $next
     # If the current directory equals the next directory, return.
     [[ $current == $next ]] && return || local current=$next
-    # If an enter script is found in the current directory, return it.
-    [ -f $current/.enter ] && echo $current
   done
 }
 
@@ -84,16 +87,16 @@ _autoenv_find_enter() {
 # setup local environments for directory and its subdirectories.
 _autoenv_chpwd() {
   local entered
-  # Loop over the entered directory stack.
-  for entered in $_autoenv_entered; do
+  # Loop over the reversed entered directory array.
+  for entered in ${(aO)_autoenv_entered}; do
     # If the the current directory was previously entered then exit.
-    # TODO: Verify what this condition expression actually does.
     ! [[ $PWD/ == $entered/* ]] && _autoenv_exit $entered
   done
-  # Find the nearest enter script directory.
-  local enter=`_autoenv_find_enter`
-  # If the enter directory exists, enter it.
-  [ -d "$enter" ] && _autoenv_enter $enter
+  # Find all enter script directories, store them in an array.
+  local enter_dirs=(`_autoenv_find_enter_directories`)
+  # Loop over reversed enter script directories array, so enter scripts found
+  # last are sourced first, then source all enter scripts.
+  for enter in ${(aO)enter_dirs}; do _autoenv_enter $enter; done
 }
 
 # Register the autoenv chpwd hook.