How does one merge texts together? like a version control system would?

Question

Wikipedia says this is pretty good: http://en.wikipedia.org/wiki/Merge_(revision_control)#Three-way_merge

But how does one implement that? or are there any gems / plugins for Ruby on Rails that will handle that for me?

My situation:
• I have base text
• changes from person A
• changes from person B
• both changes should be included and not overriding the other

any directions I could be pointed in? thanks!

Answer 1

I think you should look at the merge3 gem again [source].

This small example explains it:

require 'rubygems'
require 'merge3'

start = <<TEXT
This is the baseline.
The start.
The end.
TEXT
changed_A = <<TEXT
This is the baseline.
The start (changed by A).
The end.
TEXT
changed_B = <<TEXT
This is the baseline.
The start.
B added this line.
The end.
TEXT

result = Merge3::three_way(start, changed_A, changed_B)

puts result

The output it generates is:

This is the baseline.
The start (changed by A).
B added this line.
The end.

I am not sure how it handles merge conflicts, and since it is supposed to handle 3-way merges of files, it seems to be line-based. If that is a problem (as your example tries to compare simple string), you could add a newline between every character.

Hope this helps.

Answer 2

If you're storing versioned text that you want to be able to merge, then it sounds like you have a perfect use case for calling a version control system. Store the text in files and call the VCS for version control operations (perhaps the Git or Grit gems would be helpful).