This specifies a new merge strategy called railsschema, along with the necessary command that Git needs to execute to resolve conflicts. The command itself is just a piece of Ruby code that figures out which schema.rb is the most recent one.

.gitattributes_example

[merge "railsschema"]
        name = newer Rails schema version
        driver = "ruby -e '\n\
                system %(git), %(merge-file), %(--marker-size=%L), %(%A), %(%O), %(%B)\n\
                b = File.read(%(%A))\n\
                b.sub!(/^<+ .*\\nActiveRecord::Schema\\.define.:version => (\\d+). do\\n=+\\nActiveRecord::Schema\\.define.:version => (\\d+). do\\n>+ .*/) do\n\
                  %(ActiveRecord::Schema.define(:version => #{[$1, $2].max}) do)\n\
                end\n\
                File.open(%(%A), %(w)) {|f| f.write(b)}\n\
                exit 1 if b.include?(%(<)*%L)'"