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 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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 18 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);
 }