[PATCH v2 1/4] line-log: fix crash when combined with pickaxe options

["Michael Montalbo via GitGitGadget" <gitgitgadget@gmail.com>]

From: Michael Montalbo <mmontalbo@gmail.com>

queue_diffs() passes the caller's diff_options, which may carry
user-specified pickaxe state, to diff_tree_oid() and diffcore_std()
when detecting renames for line-level history tracking.  When pickaxe
options are present on the command line (-G and -S to filter by text
pattern, --find-object to filter by object identity), diffcore_std()
also runs diffcore_pickaxe(), which may discard diff pairs that are
relevant for rename detection.  Losing those pairs breaks rename
following.

Before a2bb801f6a (line-log: avoid unnecessary full tree diffs,
2019-08-21), this silently truncated history at rename boundaries.
That commit moved filter_diffs_for_paths() inside the rename-
detection block, so it only runs when diff_might_be_rename() returns
true.  When pickaxe discards a rename pair, the rename goes
undetected, and a deletion pair at a subsequent commit passes
through uncleaned, reaching process_diff_filepair() with an invalid
filespec and triggering an assertion failure.

Fix this by building a private diff_options for the rename-detection
path inside queue_diffs(), following the same pattern used by blame's
find_rename().  This isolates the rename machinery from unrelated
user-specified options.

Reported-by: Matthew Hughes <matthewhughes934@gmail.com>
Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>
---
 line-log.c          | 22 ++++++++++++++----
 t/t4211-line-log.sh | 55 +++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+), 4 deletions(-)

diff --git a/line-log.c b/line-log.c
index eeaf68454e..9d12ece181 100644
--- a/line-log.c
+++ b/line-log.c
@@ -858,15 +858,29 @@ static void queue_diffs(struct line_log_data *range,
 	diff_queue_clear(&diff_queued_diff);
 	diff_tree_oid(parent_tree_oid, tree_oid, "", opt);
 	if (opt->detect_rename && diff_might_be_rename()) {
+		struct diff_options rename_opts;
+
+		/*
+		 * Build a private diff_options for rename detection so
+		 * that any user-specified options on the original opts
+		 * (e.g. pickaxe) cannot discard diff pairs needed for
+		 * rename tracking.  Similar to blame's find_rename().
+		 */
+		repo_diff_setup(opt->repo, &rename_opts);
+		rename_opts.flags.recursive = 1;
+		rename_opts.detect_rename = opt->detect_rename;
+		rename_opts.rename_score = opt->rename_score;
+		rename_opts.output_format = DIFF_FORMAT_NO_OUTPUT;
+		diff_setup_done(&rename_opts);
+
 		/* must look at the full tree diff to detect renames */
-		clear_pathspec(&opt->pathspec);
 		diff_queue_clear(&diff_queued_diff);
-
-		diff_tree_oid(parent_tree_oid, tree_oid, "", opt);
+		diff_tree_oid(parent_tree_oid, tree_oid, "", &rename_opts);
 
 		filter_diffs_for_paths(range, 1);
-		diffcore_std(opt);
+		diffcore_std(&rename_opts);
 		filter_diffs_for_paths(range, 0);
+		diff_free(&rename_opts);
 	}
 	move_diff_queue(queue, &diff_queued_diff);
 }
diff --git a/t/t4211-line-log.sh b/t/t4211-line-log.sh
index 0a7c3ca42f..659a943aa1 100755
--- a/t/t4211-line-log.sh
+++ b/t/t4211-line-log.sh
@@ -367,4 +367,59 @@ test_expect_success 'show line-log with graph' '
 	test_cmp expect actual
 '
 
+test_expect_success 'setup for -L with -G/-S/--find-object and a merge with rename' '
+	git checkout --orphan pickaxe-rename &&
+	git reset --hard &&
+
+	echo content >file &&
+	git add file &&
+	git commit -m "add file" &&
+
+	git checkout -b pickaxe-rename-side &&
+	git mv file renamed-file &&
+	git commit -m "rename file" &&
+
+	git checkout pickaxe-rename &&
+	git commit --allow-empty -m "diverge" &&
+	git merge --no-edit pickaxe-rename-side &&
+
+	git mv renamed-file file &&
+	git commit -m "rename back"
+'
+
+test_expect_success '-L -G does not crash with merge and rename' '
+	git log --format="%s" --no-patch -L 1,1:file -G "." >actual
+'
+
+test_expect_success '-L -S does not crash with merge and rename' '
+	git log --format="%s" --no-patch -L 1,1:file -S content >actual
+'
+
+test_expect_success '-L --find-object does not crash with merge and rename' '
+	git log --format="%s" --no-patch -L 1,1:file \
+		--find-object=$(git rev-parse HEAD:file) >actual
+'
+
+# Commit-level filtering with pickaxe does not yet work for -L.
+# show_log() prints the commit header before diffcore_std() runs
+# pickaxe, so commits cannot be suppressed even when no diff pairs
+# survive filtering.  Fixing this would require deferring show_log()
+# until after diffcore_std(), which is a larger restructuring of the
+# log-tree output pipeline.
+test_expect_failure '-L -G should filter commits by pattern' '
+	git log --format="%s" --no-patch -L 1,1:file -G "nomatch" >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_failure '-L -S should filter commits by pattern' '
+	git log --format="%s" --no-patch -L 1,1:file -S "nomatch" >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_failure '-L --find-object should filter commits by object' '
+	git log --format="%s" --no-patch -L 1,1:file \
+		--find-object=$ZERO_OID >actual &&
+	test_must_be_empty actual
+'
+
 test_done
-- 
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