Hi Brett. I don't have Ruby installed, so I came up with a version that used `sed` instead. Here's a breakdown of what the function does:

* Strips white spaces from the input parameter.
* Converts input parameter to have [^/]* after every character.
* Uses the resulting pattern to find a match between two /'s (while also prefixing the pattern with [^/]*).
* If a match is found, return everything up to the end of the match, stripping off any trailing test.

function _up()
{
local rx
rx=$(echo "$1" | sed -e "s/\s\+//g" -e "s/\(.\)/\1[^\/]*/g")
echo -n $(pwd | sed -e "s/\(.*\/[^\/]*${rx}\)\/.*/\1/")
}

Sidenote: speaking of bashmarks... Not sure it's under active maintenance anymore. :( It has a few important pull requests lingering.

Your sentaku link is not quite correct...

If used with ZSH, there will be an error with this line:

updir=`echo $PWD | ruby -e "print STDIN.read.sub(/(.*\/$rx[^\/]*\/).*/i,'\1')"`

To fix it, you need to surround $rx with curly braces:

updir=`echo $PWD | ruby -e "print STDIN.read.sub(/(.*\/${rx}[^\/]*\/).*/i,'\1')"`

Here is an improvement for gt our sysadmin wrote to avoid jumping to ~ if you are not within a git repository and to avoid strange output on opening a terminal:

alias gt='cd $(git rev-parse --show-toplevel 2>/dev/null || (echo "."; echo "Not within a git repository" >&2))'