drop dirname in favor of native Bash strings (1 of 2)

Convert `var=${dirname $filename)` to `var="${filename%/*}` in cases where there is no ambiguity.

Make sure that the path in `$BASH_IT` is absolute because this path gets embedded in the template `.bash_profile` file if selected by the user.

plugins/available/z_autoenv.plugin.bash

@@ -11,7 +11,7 @@ autoenv_init()
   typeset target home _file
   typeset -a _files
   target=$1
-  home="$(dirname "$HOME")"
+  home="${HOME%/*}"
 
   _files=( $(
     while [[ "$PWD" != "/" && "$PWD" != "$home" ]]