This test isn't that useful.  The better way to evaluate diff
algorithm performance is to run `jgit debug-diff-algorithms` over
real-world repositories, such as linux-2.6.git.  Whenever we modify
an algorithm we should manually verify that its runtime performance
doesn't get any worse than it already is.

Change-Id: I0beed3a5a8a537c958a5a6438a1283f97fa2097a
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Each algorithm should produce a particular number of results
given one of the standard inputs used during the performance
tests.  To help ensure those tests are accurate, assert that
the edit list length is correct.

Change-Id: I292f8fde0cec6a60a75ce09e70814a00ca47cb99
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

For certain tiny input sequences, every DiffAlgorithm should produce
exactly the same results, as there should be no ambiguity.  Package
these up in an abstract TestCase that algorithms can extend from in
order to perform basic validation of their implementation.

Since these tests are more complete than what we used to have for
the MyersDiff algorithm, throw away Johannes' tests and only use
this new package.

Change-Id: I9a044330887c849ad4c78aa5c7aa04c783c10252
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

This makes it easier to parametrize DiffFormatter with a different
implementation, as we later plan to add PatienceDiff to JGit.

Change-Id: Id35ef478d5fa20fe10a1ba297f9436fd7adde9ce
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Instead of making the sequence itself responsible for the equivalence
function, use an external function that is supplied by the caller.
This cleans up the code because we now say cmp.equals(a, ai, b, bi)
instead of a.equals(ai, b, bi).

This refactoring also removes the odd concept of creating different
types of sequences to have different behaviors for whitespace
ignoring.  Instead DiffComparator now supports singleton functions
that apply a particular equivalence algorithm to a type of sequence.

Change-Id: I559f494d81cdc6f06bfb4208f60780c0ae251df9
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Bug: 291083
Eclipse-CQ: 3559
Change-Id: I5a10946637438052e7596489b9f9de3a0c6b2066
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Per CQ 3448 this is the initial contribution of the JGit project
to eclipse.org.  It is derived from the historical JGit repository
at commit 3a2dd9921c.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>