Expose a more generic DiffAlgorithm property in CompareOptions

[nulltoken]

Following #1039 and in order to avoid future breaking changes maybe would it be wise to expose a property accepting an enum of Diff algorithms (Meyer, Minimal, ...).

/cc @dmalikov

• Add new property
• Obsolete current property
• Implement minimal tests to cover each algorithm

[dmalikov]

Ok, sure, why not

[nulltoken]

Ready for review

[Therzok]

(Default = Algorithm.Meyers)

[nulltoken]

Fixed

[Therzok]

Other than missing implementation for minimal diff, that's all I can say.

[nulltoken]

@Therzok I've been refraining from implementing the --minimal algo as I haven't found a proper concise example of its output (which should differ from what would be computed through Meyer or Patience).

Any idea?

[Therzok]

Only seems to do things for big diffs. I just did:

➜  monodevelop git:(master) git diff --diff-algorithm=minimal HEAD~600 HEAD | wc -l
   77496
➜  monodevelop git:(master) git diff --diff-algorithm=myers HEAD~600 HEAD | wc -l
   79049

Returned same results until around ~600 commits, and I tracked down what changed the stuff. It seems to be XML that's the culprit of making minimal better, but only in a big diff context.

Here's the diff between the two.

https://gist.github.com/Therzok/0f1f127ab2c9bb95681b

They make chrome choke when trying to gist them:
https://www.dropbox.com/s/dsmizfjupayh6sm/diff-min.diff?dl=0
https://www.dropbox.com/s/rh7kfxo5b9w4fwo/diff-myers.diff?dl=0

Differences also happen in libgit2sharp repo with ~300 commits from HEAD.

➜  libgit2sharp git:(therzok/mono4) git diff --diff-algorithm=minimal HEAD~300 HEAD | wc -l
   38993
➜  libgit2sharp git:(therzok/mono4) git diff --diff-algorithm=myers HEAD~300 HEAD | wc -l
   39058

https://gist.github.com/Therzok/8c8a87c4586d428513b8

[Therzok]

In short it only affects huge diffs. This would be useful for someone diffing HEAD to 1 year prior, but not many people do this. So it would be best to keep it.

Short things short: minimal is just myers with better diffs for huge stuff.

Edit: The time difference is actually not noticeable.

[nulltoken]

Proposal: Merge this and log an up-for-grabs issue for Minimal implementation. Eventually @dmalikov's question may get an answer...

[nulltoken]

Published as NuGet pre-release package LibGit2Sharp.0.22.0-pre20150527180327