Add module "bd".

modules/bd/Readme.md

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+# bd
+Jump back to a specific directory, without doing `cd ../../..`
+
+This is simply [bd](https://github.com/Tarrasch/zsh-bd) ported to a prezto module.
+
+For further information, e.g. a usage animation, I refer to the [original repository](https://github.com/Tarrasch/zsh-bd).
+
+## Usage
+```zsh
+$ mkdir -p a/b/c/d
+$ cd a/b/c/d
+$ bd b
+$ ls
+c
+```
+
+## Acknowledgements
+Thanks to [@Tarrasch](https://github.com/Tarrasch) for the zsh implementation of bd!

modules/bd/init.zsh

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+bd () {
+  (($#<1)) && {
+    print -- "usage: $0 <name-of-any-parent-directory>"
+    return 1
+  } >&2
+  # Get parents (in reverse order)
+  local parents
+  local num=${#${(ps:/:)${PWD}}}
+  local i
+  for i in {$((num+1))..2}
+  do
+    parents=($parents "`echo $PWD | cut -d'/' -f$i`")
+  done
+  parents=($parents "/")
+  # Build dest and 'cd' to it
+  local dest="./"
+  local parent
+  foreach parent (${parents})
+  do
+    if [[ $1 == $parent ]]
+    then
+      cd $dest
+      return 0
+    fi
+    dest+="../"
+  done
+  print -- "bd: Error: No parent directory named '$1'"
+  return 1
+}
+_bd () {
+  # Get parents (in reverse order)
+  local num=${#${(ps:/:)${PWD}}}
+  local i
+  for i in {$((num+1))..2}
+  do
+    reply=($reply "`echo $PWD | cut -d'/' -f$i`")
+  done
+  reply=($reply "/")
+}
+compctl -V directories -K _bd bd