From 5533580575b06689132aae65de8faa3ded1634ca Mon Sep 17 00:00:00 2001 From: Michael Montalbo Date: Sun, 14 Jun 2026 18:59:23 +0000 Subject: [PATCH] blame: consult diff process for no-hunk detection When a diff process is configured via diff..process, consult it during blame's per-commit diffing. If the process returns no hunks for a commit's changes to a file, treat the commit as having no changes, causing blame to attribute lines to earlier commits. The consultation happens at the pass_blame_to_parent() callsite using diff_process_fill_hunks(), matching how builtin_diff() in diff.c uses the same function. A new diff_hunks_xpp() variant accepts a pre-populated xpparam_t so callers can pass external hunks, while the existing diff_hunks() retains its original signature and behavior. The copy-detection callsite is unaffected since it does not use the diff process. The subprocess is long-running (one startup cost amortized across the blame traversal), but each commit in the file's history incurs a round-trip to the tool. Signed-off-by: Michael Montalbo Signed-off-by: Junio C Hamano --- blame.c | 40 +++++++++++---- t/t4080-diff-process.sh | 105 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 136 insertions(+), 9 deletions(-) diff --git a/blame.c b/blame.c index 977cbb7097..354e6c15f4 100644 --- a/blame.c +++ b/blame.c @@ -19,6 +19,8 @@ #include "tag.h" #include "trace2.h" #include "blame.h" +#include "diff-process.h" +#include "xdiff-interface.h" #include "alloc.h" #include "commit-slab.h" #include "bloom.h" @@ -314,17 +316,25 @@ static struct commit *fake_working_tree_commit(struct repository *r, +static int diff_hunks_xpp(mmfile_t *file_a, mmfile_t *file_b, + xdl_emit_hunk_consume_func_t hunk_func, + void *cb_data, xpparam_t *xpp) +{ + xdemitconf_t xecfg = {0}; + xdemitcb_t ecb = {NULL}; + + xecfg.hunk_func = hunk_func; + ecb.priv = cb_data; + return xdi_diff(file_a, file_b, xpp, &xecfg, &ecb); +} + static int diff_hunks(mmfile_t *file_a, mmfile_t *file_b, xdl_emit_hunk_consume_func_t hunk_func, void *cb_data, int xdl_opts) { xpparam_t xpp = {0}; - xdemitconf_t xecfg = {0}; - xdemitcb_t ecb = {NULL}; xpp.flags = xdl_opts; - xecfg.hunk_func = hunk_func; - ecb.priv = cb_data; - return xdi_diff(file_a, file_b, &xpp, &xecfg, &ecb); + return diff_hunks_xpp(file_a, file_b, hunk_func, cb_data, &xpp); } static const char *get_next_line(const char *start, const char *end) @@ -1943,6 +1953,7 @@ static void pass_blame_to_parent(struct blame_scoreboard *sb, struct blame_origin *parent, int ignore_diffs) { mmfile_t file_p, file_o; + xpparam_t xpp = {0}; struct blame_chunk_cb_data d; struct blame_entry *newdest = NULL; @@ -1961,10 +1972,21 @@ static void pass_blame_to_parent(struct blame_scoreboard *sb, &sb->num_read_blob, ignore_diffs); sb->num_get_patch++; - if (diff_hunks(&file_p, &file_o, blame_chunk_cb, &d, sb->xdl_opts)) - die("unable to generate diff (%s -> %s)", - oid_to_hex(&parent->commit->object.oid), - oid_to_hex(&target->commit->object.oid)); + xpp.flags = sb->xdl_opts; + /* + * If the diff process considers the files equivalent, + * skip the diff so blame looks past this commit. + */ + if (diff_process_fill_hunks(&sb->revs->diffopt, target->path, + &file_p, &file_o, &xpp) + != DIFF_PROCESS_EQUIVALENT) { + if (diff_hunks_xpp(&file_p, &file_o, blame_chunk_cb, + &d, &xpp)) + die("unable to generate diff (%s -> %s)", + oid_to_hex(&parent->commit->object.oid), + oid_to_hex(&target->commit->object.oid)); + } + free(xpp.external_hunks); /* The rest are the same as the parent */ blame_chunk(&d.dstq, &d.srcq, INT_MAX, d.offset, INT_MAX, 0, parent, target, 0); diff --git a/t/t4080-diff-process.sh b/t/t4080-diff-process.sh index df4d08e31f..9fc3c01eec 100755 --- a/t/t4080-diff-process.sh +++ b/t/t4080-diff-process.sh @@ -445,4 +445,109 @@ test_expect_success 'diff process skipped when tool omits capability' ' test_must_be_empty stderr ' +# +# Blame integration. +# + +test_expect_success 'blame uses tool-provided hunks' ' + cat >blame-hunk.c <<-\EOF && + line1 + line2 + line3 + line4 + original5 + original6 + line7 + line8 + line9 + line10 + EOF + git add blame-hunk.c && + git commit -m "add blame-hunk.c" && + ORIG=$(git rev-parse --short HEAD) && + + cat >blame-hunk.c <<-\EOF && + line1 + line2 + line3 + line4 + changed5 + changed6 + line7 + line8 + changed9 + changed10 + EOF + git add blame-hunk.c && + git commit -m "change blame-hunk.c" && + CHANGE=$(git rev-parse --short HEAD) && + + # With fixed-hunk mode the tool reports only lines 5-6 as changed, + # so blame should attribute lines 9-10 to the original commit + # even though the builtin diff would show them as changed. + git -c diff.cdiff.process="$BACKEND --mode=fixed-hunk" \ + blame blame-hunk.c >actual && + sed -n "9p" actual >line9 && + sed -n "10p" actual >line10 && + test_grep "$ORIG" line9 && + test_grep "$ORIG" line10 && + sed -n "5p" actual >line5 && + sed -n "6p" actual >line6 && + test_grep "$CHANGE" line5 && + test_grep "$CHANGE" line6 +' + +test_expect_success 'blame skips commits with no hunks from diff process' ' + cat >blame.c <<-\EOF && + int main(void) { + return 0; + } + EOF + git add blame.c && + git commit -m "add blame.c" && + ORIG_COMMIT=$(git rev-parse --short HEAD) && + + cat >blame.c <<-\EOF && + int main(void) + { + return 0; + } + EOF + git add blame.c && + git commit -m "reformat blame.c" && + BLAME_COMMIT=$(git rev-parse --short HEAD) && + + # Without no-hunks mode, blame attributes the change. + git blame blame.c >without && + test_grep "$BLAME_COMMIT" without && + + # With no-hunks mode, the process considers the files equivalent + # and blame skips the reformat commit, attributing to the original. + git -c diff.cdiff.process="$BACKEND --mode=no-hunks" \ + blame blame.c >with && + test_grep ! "$BLAME_COMMIT" with && + test_grep "$ORIG_COMMIT" with +' + +test_expect_success 'blame --no-ext-diff bypasses diff process' ' + test_when_finished "rm -f backend.log" && + git -c diff.cdiff.process="$BACKEND --mode=no-hunks --log=backend.log" \ + blame --no-ext-diff blame.c >actual && + # Without the process, blame attributes the reformat commit normally. + test_grep "$BLAME_COMMIT" actual && + test_path_is_missing backend.log +' + +test_expect_success 'blame --no-ext-diff uses builtin hunks' ' + # fixed-hunk mode would narrow blame to lines 5-6, but + # --no-ext-diff should bypass it and use the builtin diff. + test_when_finished "rm -f backend.log" && + git -c diff.cdiff.process="$BACKEND --mode=fixed-hunk --log=backend.log" \ + blame --no-ext-diff blame-hunk.c >actual && + # Builtin diff attributes lines 9-10 to the change commit. + sed -n "9p" actual >line9 && + test_grep "$CHANGE" line9 && + test_path_is_missing backend.log +' + test_done