David Kastrup <dak@xxxxxxx> writes: > 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/> The only thing that remotely hints why we thought a non-zero context was a good idea was this: http://thread.gmane.org/gmane.comp.version-control.git/28336/focus=28580 in which I said: | we may need to use a handful surrounding context lines for | better identification of copy source by the "ciff" algorithm but | that is a minor implementation detail. But I do not think the amount of context affects the quality of the match. So it could be that it was completely a misguided attempt since the very beginning, cee7f245 (git-pickaxe: blame rewritten., 2006-10-19), which allowed the caller to specify context when calling compare_buffer(), the function that corresponds to diff_hunks() in today's code. > --- > builtin/blame.c | 7 +++---- > 1 file changed, 3 insertions(+), 4 deletions(-) I totally forgot about the discussion around $gmane/255289; thanks for bringing this back again. As usual, we'd need your sign-off to use this patch. Thanks. > 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 */ -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html