Subject: [PATCH] Require 0 context lines in git-blame algorithm

From: David Kastrup <[email-masked]>
Date: Fri, 27 May 2016 16:16:32 +0200

Previously, the core part of git blame -M required 1 context line.
There is no rationale to be found in the code (one guess would be that
the old blame algorithm was unable to deal with immediately adjacent
regions), and it causes artifacts like discussed in the thread
<URL:http://thread.gmane.org/gmane.comp.version-control.git/255289/>
---
 builtin/blame.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/builtin/blame.c b/builtin/blame.c
index 21f42b0..a3f6874 100644
--- a/builtin/blame.c
+++ b/builtin/blame.c
@@ -134,7 +134,7 @@ struct progress_info {
 	int blamed_lines;
 };
 
-static int diff_hunks(mmfile_t *file_a, mmfile_t *file_b, long ctxlen,
+static int diff_hunks(mmfile_t *file_a, mmfile_t *file_b,
 		      xdl_emit_hunk_consume_func_t hunk_func, void *cb_data)
 {
 	xpparam_t xpp = {0};
@@ -142,7 +142,6 @@ static int diff_hunks(mmfile_t *file_a, mmfile_t *file_b, long ctxlen,
 	xdemitcb_t ecb = {NULL};
 
 	xpp.flags = xdl_opts;
-	xecfg.ctxlen = ctxlen;
 	xecfg.hunk_func = hunk_func;
 	ecb.priv = cb_data;
 	return xdi_diff(file_a, file_b, &xpp, &xecfg, &ecb);
@@ -980,7 +979,7 @@ static void pass_blame_to_parent(struct scoreboard *sb,
 	fill_origin_blob(&sb->revs->diffopt, target, &file_o);
 	num_get_patch++;
 
-	if (diff_hunks(&file_p, &file_o, 0, blame_chunk_cb, &d))
+	if (diff_hunks(&file_p, &file_o, blame_chunk_cb, &d))
 		die("unable to generate diff (%s -> %s)",
 		    oid_to_hex(&parent->commit->object.oid),
 		    oid_to_hex(&target->commit->object.oid));
@@ -1129,7 +1128,7 @@ static void find_copy_in_blob(struct scoreboard *sb,
 	 * file_p partially may match that image.
 	 */
 	memset(split, 0, sizeof(struct blame_entry [3]));
-	if (diff_hunks(file_p, &file_o, 1, handle_split_cb, &d))
+	if (diff_hunks(file_p, &file_o, handle_split_cb, &d))
 		die("unable to generate diff (%s)",
 		    oid_to_hex(&parent->commit->object.oid));
 	/* remainder, if any, all match the preimage */
-- 
2.7.4