Reproduction steps

Old tree has files a and c with the same content, new tree only has c/d.

char *paths[] = { "a", "c/*" };

opts.flags = GIT_DIFF_INCLUDE_TYPECHANGE_TREES;
opts.pathspec.strings = paths;
opts.pathspec.count = 2;

git_diff_tree_to_tree(&diff, repo, old_tree, new_tree, &opts);

Expected behavior

D a and A c/d.

Actual behavior

T a (100644 -> 040000) and A c/d.

handle_unmatched_old_item adds a delta for c and then uses diff_delta__last_for_item to turn it into a typechange. Here the pathspec filters out c, so no delta is added, and the last delta is actually the one for a. diff_delta__last_for_item only compares ids, and a and c have the same id, so the delta for a gets changed. A notify callback that skips the delta causes the same thing, and handle_unmatched_new_item has the same pattern.

Version of libgit2 (release number or SHA1)

main (0551dfd)

Operating system(s) tested

Linux