Merge branch 'jc/maint-reset-unmerged-path' into maint

* jc/maint-reset-unmerged-path:
  reset [<commit>] paths...: do not mishandle unmerged paths

builtin/reset.c

@@ -162,7 +162,7 @@ static void update_index_from_diff(struct diff_queue_struct *q,
 
 	for (i = 0; i < q->nr; i++) {
 		struct diff_filespec *one = q->queue[i]->one;
-		if (one->mode) {
+		if (one->mode && !is_null_sha1(one->sha1)) {
 			struct cache_entry *ce;
 			ce = make_cache_entry(one->mode, one->sha1, one->path,
 				0, 0);

diff-lib.c

@@ -379,7 +379,8 @@ static void do_oneway_diff(struct unpack_trees_options *o,
 	if (cached && idx && ce_stage(idx)) {
 		struct diff_filepair *pair;
 		pair = diff_unmerge(&revs->diffopt, idx->name);
-		fill_filespec(pair->one, idx->sha1, idx->ce_mode);
+		if (tree)
+			fill_filespec(pair->one, tree->sha1, tree->ce_mode);
 		return;
 	}
 

t/t7102-reset.sh

@@ -429,6 +429,21 @@ test_expect_success '--mixed refreshes the index' '
 	test_i18ncmp expect output
 '
 
+test_expect_success 'resetting specific path that is unmerged' '
+	git rm --cached file2 &&
+	F1=$(git rev-parse HEAD:file1) &&
+	F2=$(git rev-parse HEAD:file2) &&
+	F3=$(git rev-parse HEAD:secondfile) &&
+	{
+		echo "100644 $F1 1	file2" &&
+		echo "100644 $F2 2	file2" &&
+		echo "100644 $F3 3	file2"
+	} | git update-index --index-info &&
+	git ls-files -u &&
+	test_must_fail git reset HEAD file2 &&
+	git diff-index --exit-code --cached HEAD
+'
+
 test_expect_success 'disambiguation (1)' '
 
 	git reset --hard &&