From ffffb987fcd3b3d6b88aceed87000ef4a5b6114e Mon Sep 17 00:00:00 2001
From: Antonin Delpeuch <antonin@delpeuch.eu>
Date: Mon, 17 Nov 2025 08:04:32 +0000
Subject: blame: make diff algorithm configurable

The diff algorithm used in 'git-blame(1)' is set to 'myers',
without the possibility to change it aside from the `--minimal` option.

There has been long-standing interest in changing the default diff
algorithm to "histogram", and Git 3.0 was floated as a possible occasion
for taking some steps towards that:

https://lore.kernel.org/git/xmqqed873vgn.fsf@gitster.g/

As a preparation for this move, it is worth making sure that the diff
algorithm is configurable where useful.

Make it configurable in the `git-blame(1)` command by introducing the
`--diff-algorithm` option and make honor the `diff.algorithm` config
variable. Keep Myers diff as the default.

Signed-off-by: Antonin Delpeuch <antonin@delpeuch.eu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/diff-algorithm-option.adoc | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
 create mode 100644 Documentation/diff-algorithm-option.adoc

(limited to 'Documentation/diff-algorithm-option.adoc')

diff --git a/Documentation/diff-algorithm-option.adoc b/Documentation/diff-algorithm-option.adoc
new file mode 100644
index 0000000000..8e3a0b63d7
--- /dev/null
+++ b/Documentation/diff-algorithm-option.adoc
@@ -0,0 +1,20 @@
+`--diff-algorithm=(patience|minimal|histogram|myers)`::
+	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.
+   `patience`;;
+	Use "patience diff" algorithm when generating patches.
+   `histogram`;;
+	This algorithm extends the patience algorithm to "support
+	low-occurrence common elements".
+--
++
+For instance, if you configured the `diff.algorithm` variable to a
+non-default value and want to use the default one, then you
+have to use `--diff-algorithm=default` option.
-- 
cgit v1.2.3

