coda shell script. Download that script by clicking on "raw" and save it somewhere on your $PATH as "coda". Then make it executable (chmod +x /path/to/coda).

coda.sh

#!/bin/sh
#
# Shell script to open files or folders with Coda.app

# Based on a script by Wout Mertens and suggestions from Laurent Bihanic.
# The original version is the fault of Benji Fisher, 16 May 2005 (with
# modifications by Nico Weber and Bjorn Winckler, Aug 13 2007). Originally
# released as  the "mvim" shell script of MacVim.app.

# First, check "All the Usual Suspects" for the location of the Coda.app
# bundle. You can short-circuit this by setting the CODA_APP_DIR environment
# variable or by un-commenting and editing the following line:
# CODA_APP_DIR=/Applications

if [ -z "$CODA_APP_DIR" ]
then
  myDir="`dirname "$0"`"
  myAppDir="$myDir/../Applications"
  for i in ~/Applications $myDir $myAppDir /Applications /Applications/Utilities; do
    if [ -x "$i/Coda.app" ]; then
      CODA_APP_DIR="$i"
      break
    fi
  done
fi
if [ -z "$CODA_APP_DIR" ]
then
  echo "Sorry, cannot find Coda.app. Try setting the CODA_APP_DIR environment variable to the directory containing Coda.app."
  exit 1
fi

binary="$CODA_APP_DIR/Coda.app"

if [ "$1" ]; then
  open -a "$binary" ${1:+"$@"}
else
  echo "Usage: coda [file ...]"
fi