Use git_buf for path storage instead of stack-based buffers

This converts virtually all of the places that allocate GIT_PATH_MAX
buffers on the stack for manipulating paths to use git_buf objects
instead.  The patch is pretty careful not to touch the public API
for libgit2, so there are a few places that still use GIT_PATH_MAX.

This extends and changes some details of the git_buf implementation
to add a couple of extra functions and to make error handling easier.

This includes serious alterations to all the path.c functions, and
several of the fileops.c ones, too.  Also, there are a number of new
functions that parallel existing ones except that use a git_buf
instead of a stack-based buffer (such as git_config_find_global_r
that exists alongsize git_config_find_global).

This also modifies the win32 version of p_realpath to allocate whatever
buffer size is needed to accommodate the realpath instead of hardcoding
a GIT_PATH_MAX limit, but that change needs to be tested still.

1 files changed, 4 insertions, 3 deletions

diff --git a/tests-clay/clay_main.c b/tests-clay/clay_main.c
index 409ce7643..f0ec50966 100644
--- a/tests-clay/clay_main.c
+++ b/tests-clay/clay_main.c
@@ -171,7 +171,8 @@ static const struct clay_func _clay_cb_core_path[] = {
 	{"1", &test_core_path__1},
 	{"2", &test_core_path__2},
 	{"5", &test_core_path__5},
-	{"6", &test_core_path__6}
+	{"6", &test_core_path__6},
+	{"7", &test_core_path__7}
 };
 static const struct clay_func _clay_cb_core_rmdir[] = {
     {"delete_recursive", &test_core_rmdir__delete_recursive},
@@ -351,7 +352,7 @@ static const struct clay_suite _clay_suites[] = {
         "core::path",
         {NULL, NULL},
         {NULL, NULL},
-        _clay_cb_core_path, 5
+        _clay_cb_core_path, 6
     },
 	{
         "core::rmdir",
@@ -494,7 +495,7 @@ static const struct clay_suite _clay_suites[] = {
 };
 
 static size_t _clay_suite_count = 34;
-static size_t _clay_callback_count = 113;
+static size_t _clay_callback_count = 114;
 
 /* Core test functions */
 static void