As a user I wondered what the diff algorithms are about. Offer at least
a basic explanation on the differences of the diff algorithms.
Signed-off-by: Stefan Beller <sbel...@google.com>
---
Documentation/diff-options.txt | 32 +++++++++++++++++++++++++-------
1 file changed, 25 insertions(+), 7 deletions(-)
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index f466600972f..0d765482027 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -94,16 +94,34 @@ diff" algorithm internally.
Choose a diff algorithm. The variants are as follows:
+
--
-`default`, `myers`;;
- The basic greedy diff algorithm. Currently, this is the default.
`minimal`;;
- Spend extra time to make sure the smallest possible diff is
- produced.
+ A diff as produced by the basic greedy algorithm described in
+ link:http://www.xmailserver.org/diff2.pdf[An O(ND) Difference Algorithm
and its Variations]
+`default`, `myers`;;
+ The same algorithm as `minimal`, extended with a heuristic to
+ reduce extensive searches. Currently, this is the default.
`patience`;;
- Use "patience diff" algorithm when generating patches.
+ Use "patience diff" algorithm when generating patches. This
+ matches the longest common subsequence of unique lines on
+ both sides, recursively. It obtained its name by the way the
+ longest subsequence is found, as that is a byproduct of the
+ patience sorting algorithm. If there are no unique lines left
+ it falls back to `myers`. Empirically this algorithm produces
+ a more readable output for code, but it does not garantuee
+ the shortest output.
`histogram`;;
- This algorithm extends the patience algorithm to "support
- low-occurrence common elements".
+ This algorithm re-implements the `patience` algorithm with
+ "support of low-occurrence common elements" and only picks
+ one element of the LCS for the recursion. It is often the
+ fastest, but in cornercases (when there are many longest
+ common subsequences of the same length) it produces bad
+ results as seen in:
+
+ seq 1 100 >one
+ echo 99 > two
+ seq 1 2 98 >>two
+ git diff --no-index --histogram one two
+
--
+
For instance, if you configured diff.algorithm variable to a
--
2.18.0.345.g5c9ce644c3-goog
