apply: add GIT_APPLY_CHECK

This adds an option which will check if a diff is applicable without
actually applying it; equivalent to git apply --check.

1 files changed, 7 insertions, 3 deletions

diff --git a/src/apply.c b/src/apply.c
index 04242621a..65b057c60 100644
--- a/src/apply.c
+++ b/src/apply.c
@@ -845,13 +845,17 @@ int git_apply(
 	    (error = git_reader_for_index(&post_reader, repo, postimage)) < 0)
 		goto done;
 
-	if ((error = git_repository_index(&index, repo)) < 0 ||
-	    (error = git_indexwriter_init(&indexwriter, index)) < 0)
-		goto done;
+	if (!(opts.flags & GIT_APPLY_CHECK))
+		if ((error = git_repository_index(&index, repo)) < 0 ||
+		    (error = git_indexwriter_init(&indexwriter, index)) < 0)
+			goto done;
 
 	if ((error = apply_deltas(repo, pre_reader, preimage, post_reader, postimage, diff, &opts)) < 0)
 		goto done;
 
+	if ((opts.flags & GIT_APPLY_CHECK))
+		goto done;
+
 	switch (location) {
 	case GIT_APPLY_LOCATION_BOTH:
 		error = git_apply__to_workdir(repo, diff, preimage, postimage, location, &opts);