let me start with this script (for Xcode 4.2.1),

• Open an XCode project at /this/path/project.xcodeproj (done)
• Duplicate an existing target and rename it (not implemented)
• Edit the Build Settings of the new target (done)
• Add a group to the Source and Resources section, then rename them (done)
• Add source files to the groups, and add the file to the new Target(partially)
• Close XCode (done)

!/usr/bin/osascript

# Reference: AppleScript Editor -> File -> Open Directory ... -> Xcode 4.2.1# http://vgable.com/blog/2009/04/24/how-to-check-if-an-application-is-running-with-applescript/on ApplicationIsRunning(appName)    tell application "System Events" to set appNameIsRunning to exists (processes where name is appName)    return appNameIsRunningend ApplicationIsRunningif not ApplicationIsRunning("Xcode") then    log ("Launching Xcode ...")    launch application id "com.apple.dt.Xcode"    delay 5else    log("Xcode is already running ...")end ifset project_path to "/PATH/TO/YOUR_PROJECT.xcodeproj"log ("Open an XCode project at " & project_path)set _project_name to (do shell script "echo $(basename " & project_path & ") | sed -e 's/.xcodeproj//'")log ("project_name set to " & _project_name)set _target_name to "YOUR_TARGET"tell application id "com.apple.dt.Xcode"    set _project_file to (POSIX file project_path as alias)    open _project_file    # load documentation set with path path_to_project display yes    set _workspace to active workspace document    set _project to first item of (projects of _workspace whose name = _project_name)    set _target to first item of (targets of _project whose name = _target_name)    # as this won't work, cannot event resort to system event    # duplicate _target with properties {name:_target_name & "_clone"}    # make new build configuration with data build configurations of _target with properties {name:_target_name & "_clone"}    # activate    log ("Edit the Build Settings of the new target")    set _build_configuration to first item of (build configurations of _target whose name = "Debug")    set value of build setting "PRODUCT_NAME" of _build_configuration to "KeySING"    # http://lists.apple.com/archives/xcode-users//2008/Feb/msg00497.html    log ("Add a group to the Source and Resources section, then rename them")    set _new_group_name to "groupX"    tell root group of _project        set _groups to (get groups whose name = _new_group_name)        if (length of _groups) = 0 then            set _new_group to make new group with properties {name:_new_group_name, path:_new_group_name, path type:group relative}        else            set _new_group to first item of _groups        end if        log ("Add source files to the groups, and add the file to the new Target")        tell _new_group            set _new_file_name to "whatever.h"            set _new_files to get (file references whose name = _new_file_name)            if (length of _new_files) = 0 then                # Xcode crashes                # make new file reference with properties ¬                #     {name:_new_file_name, file encoding:utf8, path type:group relative,¬                #      path:_new_file_name}            end if        end tell    end tell    log ("Close XCode")    quitend tell