diff: return diff_filepair from diff queue helpers

The `diff_addremove()` and `diff_change()` functions set up and queue
diffs, but do not return the `diff_filepair` added to the queue. In a
subsequent commit, modifications to `diff_filepair` need to occur in
certain cases after being queued.

Since the existing `diff_addremove()` and `diff_change()` are also used
for callbacks in `diff_options` as types `add_remove_fn_t` and
`change_fn_t`, modifying the existing function signatures requires
further changes. The diff options for pruning use `file_add_remove()`
and `file_change()` where file pairs do not even get queued. Thus,
separate functions are implemented instead.

Split out the queuing operations into `diff_queue_addremove()` and
`diff_queue_change()` which also return a handle to the queued
`diff_filepair`. Both `diff_addremove()` and `diff_change()` are
reimplemented as thin wrappers around the new functions.

Signed-off-by: Justin Tobler <jltobler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/diff.h b/diff.h
index 0a566f5531..63afa17e84 100644
--- a/diff.h
+++ b/diff.h
@@ -508,6 +508,31 @@ void diff_set_default_prefix(struct diff_options *options);
 
 int diff_can_quit_early(struct diff_options *);
 
+/*
+ * Stages changes in the provided diff queue for file additions and deletions.
+ * If a file pair gets queued, it is returned.
+ */
+struct diff_filepair *diff_queue_addremove(struct diff_queue_struct *queue,
+					   struct diff_options *,
+					   int addremove, unsigned mode,
+					   const struct object_id *oid,
+					   int oid_valid, const char *fullpath,
+					   unsigned dirty_submodule);
+
+/*
+ * Stages changes in the provided diff queue for file modifications.
+ * If a file pair gets queued, it is returned.
+ */
+struct diff_filepair *diff_queue_change(struct diff_queue_struct *queue,
+					struct diff_options *,
+					unsigned mode1, unsigned mode2,
+					const struct object_id *old_oid,
+					const struct object_id *new_oid,
+					int old_oid_valid, int new_oid_valid,
+					const char *fullpath,
+					unsigned dirty_submodule1,
+					unsigned dirty_submodule2);
+
 void diff_addremove(struct diff_options *,
 		    int addremove,
 		    unsigned mode,