Implement global/system file search paths

The goal of this work is to expose the search logic for "global",
"system", and "xdg" files through the git_libgit2_opts() interface.

Behind the scenes, I changed the logic for finding files to have a
notion of a git_strarray that represents a search path and to store
a separate search path for each of the three tiers of config file.
For each tier, I implemented a function to initialize it to default
values (generally based on environment variables), and then general
interfaces to get it, set it, reset it, and prepend new directories
to it.

Next, I exposed these interfaces through the git_libgit2_opts
interface, reusing the GIT_CONFIG_LEVEL_SYSTEM, etc., constants
for the user to control which search path they were modifying.
There are alternative designs for the opts interface / argument
ordering, so I'm putting this phase out for discussion.

Additionally, I ended up doing a little bit of clean up regarding
attr.h and attr_file.h, adding a new attrcache.h so the other two
files wouldn't have to be included in so many places.

1 files changed, 24 insertions, 0 deletions

diff --git a/src/attrcache.h b/src/attrcache.h
new file mode 100644
index 000000000..12cec4bfb
--- /dev/null
+++ b/src/attrcache.h
@@ -0,0 +1,24 @@
+/*
+ * Copyright (C) the libgit2 contributors. All rights reserved.
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_attrcache_h__
+#define INCLUDE_attrcache_h__
+
+#include "pool.h"
+#include "strmap.h"
+
+typedef struct {
+	int initialized;
+	git_pool pool;
+	git_strmap *files;	/* hash path to git_attr_file of rules */
+	git_strmap *macros;	/* hash name to vector<git_attr_assignment> */
+	const char *cfg_attr_file; /* cached value of core.attributesfile */
+	const char *cfg_excl_file; /* cached value of core.excludesfile */
+} git_attr_cache;
+
+extern int git_attr_cache__init(git_repository *repo);
+
+#endif