pathspec: add match_leading_pathspec variant

The do_match_pathspec() function has the DO_MATCH_LEADING_PATHSPEC
option to allow pathspecs to match when matching "src" against a
pathspec like "src/path/...". This support is not exposed by
match_pathspec, and the internal flags to do_match_pathspec are not
exposed outside of dir.c

The upcoming support for pathspecs in git diff --no-index need the
LEADING matching behavior when iterating down through a directory with
readdir.

We could try to expose the match_pathspec_with_flags to the public API.
However, DO_MATCH_EXCLUDES really shouldn't be public, and its a bit
weird to only have a few of the flags become public.

Instead, add match_leading_pathspec() as a function which sets both
DO_MATCH_DIRECTORY and DO_MATCH_LEADING_PATHSPEC when is_dir is true.

This will be used in a following change to support pathspec matching in
git diff --no-index.

Signed-off-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

dir.c

@@ -577,6 +577,16 @@ int match_pathspec(struct index_state *istate,
 					 prefix, seen, flags);
 }
 
+int match_leading_pathspec(struct index_state *istate,
+			   const struct pathspec *ps,
+			   const char *name, int namelen,
+			   int prefix, char *seen, int is_dir)
+{
+	unsigned flags = is_dir ? DO_MATCH_DIRECTORY | DO_MATCH_LEADING_PATHSPEC : 0;
+	return match_pathspec_with_flags(istate, ps, name, namelen,
+					 prefix, seen, flags);
+}
+
 /**
  * Check if a submodule is a superset of the pathspec
  */

pathspec.h

@@ -184,6 +184,12 @@ int match_pathspec(struct index_state *istate,
 		   const char *name, int namelen,
 		   int prefix, char *seen, int is_dir);
 
+/* Set both DO_MATCH_DIRECTORY and DO_MATCH_LEADING_PATHSPEC if is_dir true */
+int match_leading_pathspec(struct index_state *istate,
+			   const struct pathspec *ps,
+			   const char *name, int namelen,
+			   int prefix, char *seen, int is_dir);
+
 /*
  * Determine whether a pathspec will match only entire index entries (non-sparse
  * files and/or entire sparse directories). If the pathspec has the potential to