I\'ve always found it frustrating in WordPress that images, files, links, etc. are inserted into WordPress with an absolute URL instead of relative URL. A relative url is mu
I agree with Rup. I guess the main reason is to avoid confusion on relative paths. I think wordpress can work from scratch with relative paths but the problem might come when using multiple plugins, how the theme is configured etc.
I've once used this plugin for relative paths, when working on testing servers:
Root Relative URLs
Converts all URLs to root-relative URLs for hosting the same site on multiple IPs, easier production migration and better mobile device testing.
What i think you do is while you change domain names, the sql dump file that you have you can replace all instances of old domain name with new one. This is only option available as there are no plugins that will help you do this.
This is quickest way ..