Fix single-file ignore checks

To answer if a single given file should be ignored, the path to
that file has to be processed progressively checking that there
are no intermediate ignored directories in getting to the file
in question.  This enables that, fixing the broken old behavior,
and adds tests to exercise various ignore situations.

1 files changed, 6 insertions, 3 deletions

diff --git a/include/git2/ignore.h b/include/git2/ignore.h
index f7e04e881..964a108ce 100644
--- a/include/git2/ignore.h
+++ b/include/git2/ignore.h
@@ -54,9 +54,12 @@ GIT_EXTERN(int) git_ignore_clear_internal_rules(
 /**
  * Test if the ignore rules apply to a given path.
  *
- * This function simply checks the ignore rules to see if they would apply
- * to the given file.  This indicates if the file would be ignored regardless
- * of whether the file is already in the index or commited to the repository.
+ * This function checks the ignore rules to see if they would apply to the
+ * given file.  This indicates if the file would be ignored regardless of
+ * whether the file is already in the index or commited to the repository.
+ *
+ * One way to think of this is if you were to do "git add ." on the
+ * directory containing the file, would it be added or not?
  *
  * @param ignored boolean returning 0 if the file is not ignored, 1 if it is
  * @param repo a repository object