Update diff handling of untracked directories

When diff encounters an untracked directory, there was a shortcut
that it took which is not compatible with core git.  This makes
the default behavior no longer take that shortcut and instead look
inside the untracked directory to see if there are any untracked
files within it.  If there are not, then the directory is treated
as an ignore directory instead of an untracked directory.  This
has implications for the git_status APIs.

1 files changed, 7 insertions, 0 deletions

diff --git a/include/git2/diff.h b/include/git2/diff.h
index d9ceadf20..cc16d01b6 100644
--- a/include/git2/diff.h
+++ b/include/git2/diff.h
@@ -124,6 +124,13 @@ typedef enum {
 	 *  adds all files under the directory as IGNORED entries, too.
 	 */
 	GIT_DIFF_RECURSE_IGNORED_DIRS = (1 << 18),
+	/** For an untracked directory, diff can immediately label it UNTRACKED,
+	 *  but this differs from core Git which scans underneath for untracked
+	 *  or ignored files and marks the directory ignored unless it contains
+	 *  untracked files under it.  That search can be slow.  This flag makes
+	 *  diff skip ahead and immediately report the directory as untracked.
+	 */
+	GIT_DIFF_FAST_UNTRACKED_DIRS = (1 << 19),
 } git_diff_option_t;
 
 /**