range-diff: first rudimentary implementation

At this stage, `git range-diff` can determine corresponding commits
of two related commit ranges. This makes use of the recently introduced
implementation of the linear assignment algorithm.

The core of this patch is a straight port of the ideas of tbdiff, the
apparently dormant project at https://github.com/trast/tbdiff.

The output does not at all match `tbdiff`'s output yet, as this patch
really concentrates on getting the patch matching part right.

Note: due to differences in the diff algorithm (`tbdiff` uses the Python
module `difflib`, Git uses its xdiff fork), the cost matrix calculated
by `range-diff` is different (but very similar) to the one calculated
by `tbdiff`. Therefore, it is possible that they find different matching
commits in corner cases (e.g. when a patch was split into two patches of
roughly equal length).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/Makefile b/Makefile
index 7ff7eba..72f1688 100644
--- a/Makefile
+++ b/Makefile
@@ -925,6 +925,7 @@ LIB_OBJS += progress.o
 LIB_OBJS += prompt.o
 LIB_OBJS += protocol.o
 LIB_OBJS += quote.o
+LIB_OBJS += range-diff.o
 LIB_OBJS += reachable.o
 LIB_OBJS += read-cache.o
 LIB_OBJS += reflog-walk.o