Added jump plugin

plugins/jump/README.md

+jump
+====
+
+A port of [Jeroen Janssens' "jump" utility] [1] to the fish shell (and [Oh My Fish!] [2]).
+
+[1]: http://jeroenjanssens.com/2013/08/16/quickly-navigate-your-filesystem-from-the-command-line.html
+[2]: https://github.com/bpinto/oh-my-fish

plugins/jump/jump.fish

+function jump
+    if test (count $argv) -ne 1
+        echo "Usage: jump <MARK_NAME>"
+    else
+        if test -d $MARKPATH/$argv[1] -a -L $MARKPATH/$argv[1]
+            cd $MARKPATH/$argv[1]
+        else
+            echo "No such mark: $argv[1]"
+        end
+    end
+end

plugins/jump/jump.load

+set -x MARKPATH $HOME/.marks
+command mkdir -p $MARKPATH

plugins/jump/mark.fish

+function mark
+    if test (count $argv) -eq 1
+        command ln -s (pwd) $MARKPATH/$argv[1]
+    else if test (count $argv) -eq 2
+        if test -d $argv[2]
+            cd $argv[2]
+            command ln -s (pwd) $MARKPATH/$argv[1]
+            cd -
+        else
+            echo "$argv[2] is not a valid directory."
+        end
+    else
+        echo "Usage: mark <MARK_NAME> [DIRECTORY]"
+    end
+end

plugins/jump/marks.fish

+function marks
+    if test (count $argv) -gt 0
+        echo "Usage: marks"
+    else
+        set -l file_list (command ls $MARKPATH/)
+        set -l mark_list
+        for file in $file_list
+            if test -d $MARKPATH/$file -a -L $MARKPATH/$file
+                set mark_list $mark_list $file
+            end
+        end
+        if test (count $mark_list) -eq 0
+            echo "No marks currently defined."
+        else
+            for mark_name in $mark_list
+                echo "$mark_name -> "(realpath $MARKPATH/$mark_name)
+            end
+        end
+    end
+end

plugins/jump/unmark.fish

+function unmark
+    if test (count $argv) -eq 0
+        echo "Usage: unmark <MARK_NAME>..."
+    else
+        for mark_name in $argv
+            if test -d $MARKPATH/$mark_name -a -L $MARKPATH/$mark_name
+                command rm -i $MARKPATH/$mark_name
+            else
+                echo "No such mark: $mark_name"
+            end
+        end
+    end
+end