line-log: fix crash when combined with pickaxe options

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 a2bb801 (line-log: avoid unnecessary full tree diffs,
2019-08-21), diffcore_std() was only invoked when a rename was already
suspected, so the pickaxe interference was unlikely in practice.  That
commit restructured queue_diffs() so that filter_diffs_for_paths(),
which previously always discarded stray deletion pairs from the diff
queue, now only runs when diff_might_be_rename() signals a potential
rename.  When pickaxe breaks rename following at one commit, a later
commit may produce a deletion pair that is no longer cleaned up,
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, and calls diffcore_rename() directly since
the other stages run by diffcore_std() (pickaxe, order, break/rewrite)
are unnecessary here.

Note that this only fixes the crash.  The -G, -S, and --find-object
options still have no effect on -L output because line-log uses its
own commit-filtering logic that bypasses the normal pickaxe pipeline.
Add tests that verify the crash is fixed and mark the silent-ignore
behavior as known breakage for all three options.

Reported-by: Matthew Hughes <matthewhughes934@gmail.com>
Signed-off-by: Michael Montalbo <mmontalbo@gmail.com>

Author: mmontalbo

line-log.c

@@ -858,15 +858,28 @@ 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.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_rename(&rename_opts);
 		filter_diffs_for_paths(range, 0);
+		diff_free(&rename_opts);
 	}
 	move_diff_queue(queue, &diff_queued_diff);
 }

t/t4211-line-log.sh

@@ -367,4 +367,53 @@ 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=$(git rev-parse HEAD:file) >actual
+'
+
+test_expect_failure '-L -G should filter commits by pattern' '
+	git log --format="%s" --no-patch -L 1,1:file -G "nomatch" >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_failure '-L -S should filter commits by pattern' '
+	git log --format="%s" --no-patch -L 1,1:file -S "nomatch" >actual &&
+	test_must_be_empty actual
+'
+
+test_expect_failure '-L --find-object should filter commits by object' '
+	git log --format="%s" --no-patch -L 1,1:file \
+		--find-object=$ZERO_OID >actual &&
+	test_must_be_empty actual
+'
+
 test_done