Add public API for internal ignores

This creates a public API for adding to the internal ignores
list, which already existing but was not accessible.

This adds the new default value for core.excludesfile also.

include/git2.h

@@ -41,6 +41,7 @@
 #include "git2/checkout.h"
 
 #include "git2/attr.h"
+#include "git2/ignore.h"
 #include "git2/branch.h"
 #include "git2/refspec.h"
 #include "git2/net.h"

src/attr.c

@@ -612,6 +612,16 @@ int git_attr_cache__init(git_repository *repo)
 	if (ret < 0 && ret != GIT_ENOTFOUND)
 		return ret;
 
+	if (ret == GIT_ENOTFOUND) {
+		git_buf dflt = GIT_BUF_INIT;
+
+		ret = git_futils_find_global_file(&dflt, GIT_IGNORE_CONFIG_DEFAULT);
+		if (!ret)
+			cache->cfg_excl_file = git_buf_detach(&dflt);
+
+		git_buf_free(&dflt);
+	}
+
 	giterr_clear();
 
 	/* allocate hashtable for attribute and ignore file contents */

src/attr.h

@@ -12,6 +12,7 @@
 
 #define GIT_ATTR_CONFIG   "core.attributesfile"
 #define GIT_IGNORE_CONFIG "core.excludesfile"
+#define GIT_IGNORE_CONFIG_DEFAULT ".config/git/ignore"
 
 typedef struct {
 	int initialized;

src/ignore.c

@@ -1,3 +1,4 @@
+#include "git2/ignore.h"
 #include "ignore.h"
 #include "path.h"
 
@@ -203,3 +204,34 @@ cleanup:
 	git_attr_path__free(&path);
 	return 0;
 }
+
+int git_ignore_add_rule(
+	git_repository *repo,
+	const char *rules)
+{
+	int error;
+	git_attr_file *ign_internal;
+
+	error = git_attr_cache__internal_file(
+		repo, GIT_IGNORE_INTERNAL, &ign_internal);
+
+	if (!error && ign_internal != NULL)
+		error = parse_ignore_file(repo, rules, ign_internal);
+
+	return error;
+}
+
+int git_ignore_clear_internal_rules(
+	git_repository *repo)
+{
+	int error;
+	git_attr_file *ign_internal;
+
+	error = git_attr_cache__internal_file(
+		repo, GIT_IGNORE_INTERNAL, &ign_internal);
+
+	if (!error && ign_internal != NULL)
+		git_attr_file__clear_rules(ign_internal);
+
+	return error;
+}