Add ignore_submodules to diff options

This adds correct support for an equivalent to --ignore-submodules
in diff, where an actual ignore value can be passed to diff to
override the per submodule settings in the configuration.

This required tweaking the constants for ignore values so that
zero would not be used and could represent an unset option to the
diff.  This was an opportunity to move the submodule values into
include/git2/types.h and to rename the poorly named DEFAULT values
for ignore and update constants to RESET instead.

Now the GIT_DIFF_IGNORE_SUBMODULES flag is exactly the same as
setting the ignore_submodules option to GIT_SUBMODULE_IGNORE_ALL
(which is actually a minor change from the old behavior in that
submodules will now be treated as UNMODIFIED deltas instead of
being left out totally - if you set GIT_DIFF_INCLUDE_UNMODIFIED).

This includes tests for the various new settings.

1 files changed, 4 insertions, 1 deletions

diff --git a/include/git2/diff.h b/include/git2/diff.h
index 121c9df5c..71a8b72bf 100644
--- a/include/git2/diff.h
+++ b/include/git2/diff.h
@@ -78,7 +78,7 @@ typedef enum {
 	GIT_DIFF_IGNORE_WHITESPACE_CHANGE = (1 << 3),
 	/** Ignore whitespace at end of line */
 	GIT_DIFF_IGNORE_WHITESPACE_EOL = (1 << 4),
-	/** Exclude submodules from the diff completely */
+	/** Treat all submodules as unmodified */
 	GIT_DIFF_IGNORE_SUBMODULES = (1 << 5),
 	/** Use the "patience diff" algorithm (currently unimplemented) */
 	GIT_DIFF_PATIENCE = (1 << 6),
@@ -314,6 +314,8 @@ typedef int (*git_diff_notify_cb)(
  * - `notify_cb` is an optional callback function, notifying the consumer of
  *   which files are being examined as the diff is generated
  * - `notify_payload` is the payload data to pass to the `notify_cb` function
+ * - `ignore_submodules` overrides the submodule ignore setting for all
+ *   submodules in the diff.
  */
 typedef struct {
 	unsigned int version;      /**< version for the struct */
@@ -326,6 +328,7 @@ typedef struct {
 	git_off_t max_size;        /**< defaults to 512MB */
 	git_diff_notify_cb notify_cb;
 	void *notify_payload;
+	git_submodule_ignore_t ignore_submodules; /** << submodule ignore rule */
 } git_diff_options;
 
 #define GIT_DIFF_OPTIONS_VERSION 1