[split] Move bak plugin to oh-my-fish/plugin-bak

https://github.com/oh-my-fish/plugin-bak

plugins/bak/bak.load

-function __bak_help
-  echo -e \
-"Usage:
-  $argv[1] SOURCE..."
-end
-
-function __bak_parse_help
-  if [ (count $argv) -lt 3 ]
-    __bak_help $argv[1]
-  else
-    return 1
-  end
-end
-
-function __bak_name
-  # trim / for directories
-  set file (echo $argv[1] | sed 's/\/*$//')
-  echo "$file."(date +'%Y%m%d_%H%M%S')".bak"
-end
-
-function __bak
-  __bak_parse_help $argv
-  or begin
-    set program $argv[2]
-    for file in $argv[3..-1]
-      eval $program $file (__bak_name $file)
-    end
-  end
-end
-
-set -g __bak_re '(.*)\.[0-9]{8,8}_[0-9]{6,6}\.bak\/*$'
-
-function __is_bak
-  set file $argv[1]
-  echo "$file" | grep -Eq $__bak_re
-end
-
-function __bak_normalized
-  set file $argv[1]
-  echo "$file" | sed -E "s/$__bak_re/\1/g"
-end
-  
-function __unbak
-  __bak_parse_help $argv
-  or begin
-    set program $argv[2]
-    for file in $argv[3..-1]
-      set normalized (__bak_normalized $file)
-      if test ! -e $file
-        echo "File \"$file\" not exists! Cannot unbak \"$file\"."
-      else if not __is_bak $file
-        echo "File \"$file\" don't meet bak files convention! Cannot unbak \"$file\"."
-      else if test -e $normalized
-        echo "File \"$normalized\" exists! Cannot unbak \"$file\"."
-      else
-        eval $program $file $normalized
-      end
-    end
-  end
-end

plugins/bak/cpbak.fish

-# Function to copy files and directories (a.txt copy to a.txt.20140608_195859.bak)
-# (c) Roman Inflianskas (rominf) <infroma@gmail.com>, 2014
-
-function cpbak --description 'Copy files to make a backup copies'
-  __bak cpbak 'cp -a' $argv
-end

plugins/bak/mvbak.fish

-# Function to rename files and directories (a.txt rename to a.txt.20140608_195859.bak)
-# (c) Roman Inflianskas (rominf) <infroma@gmail.com>, 2014
-
-function mvbak --description 'Rename files to make a backup copies'
-  __bak mvbak mv $argv
-end

plugins/bak/uncpbak.fish

-# Function to copy files and directories (a.txt.20140608_195859.bak copy to a.txt)
-# (c) Roman Inflianskas (rominf) <infroma@gmail.com>, 2014
-
-function uncpbak --description 'Copy files to revert a backup copies to a normal files'
-  __unbak uncpbak 'cp -a' $argv
-end

plugins/bak/unmvbak.fish

-# Function to move files and directories (a.txt.20140608_195859.bak move to a.txt)
-# (c) Roman Inflianskas (rominf) <infroma@gmail.com>, 2014
-
-function unmvbak --description 'Move files to revert a backup copies to a normal files'
-  __unbak unmvbak mv $argv
-end