thodg/libgit2

diff --git a/include/git2/errors.h b/include/git2/errors.h
index 9b28093..7daa067 100644
--- a/include/git2/errors.h
+++ b/include/git2/errors.h
@@ -125,7 +125,7 @@ typedef enum {
 	GITERR_OS,
 	GITERR_REFERENCE,
 	GITERR_ZLIB,
-
+	GITERR_REPOSITORY,
 } git_error_class;
 
 #define GITERR_CHECK_ALLOC(ptr) if (ptr == NULL) { return -1; }
diff --git a/src/buffer.c b/src/buffer.c
index 3098f6d..dd245e2 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -70,7 +70,7 @@ int git_buf_try_grow(git_buf *buf, size_t target_size)
 
 	new_ptr = git__realloc(new_ptr, new_size);
 	if (!new_ptr)
-		return GIT_ENOMEM;
+		return -1;
 
 	buf->asize = new_size;
 	buf->ptr   = new_ptr;
@@ -100,16 +100,11 @@ void git_buf_clear(git_buf *buf)
 		buf->ptr[0] = '\0';
 }
 
-int git_buf_oom(const git_buf *buf)
+bool git_buf_oom(const git_buf *buf)
 {
 	return (buf->ptr == &git_buf__oom);
 }
 
-int git_buf_lasterror(const git_buf *buf)
-{
-	return (buf->ptr == &git_buf__oom) ? GIT_ENOMEM : GIT_SUCCESS;
-}
-
 int git_buf_set(git_buf *buf, const char *data, size_t len)
 {
 	if (len == 0 || data == NULL) {
diff --git a/src/buffer.h b/src/buffer.h
index 3cdd794..6f59dce 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -57,15 +57,10 @@ void git_buf_attach(git_buf *buf, char *ptr, size_t asize);
  * further calls to modify the buffer will fail.  Check git_buf_oom() at the
  * end of your sequence and it will be true if you ran out of memory at any
  * point with that buffer.
- * @return 0 if no error, 1 if allocation error.
- */
-int git_buf_oom(const git_buf *buf);
-
-/**
- * Just like git_buf_oom, except returns appropriate error code.
- * @return GIT_ENOMEM if allocation error, GIT_SUCCESS if not.
+ *
+ * @return false if no error, true if allocation error
  */
-int git_buf_lasterror(const git_buf *buf);
+bool git_buf_oom(const git_buf *buf);
 
 /*
  * The functions below that return int values, will return GIT_ENOMEM
diff --git a/src/commit.c b/src/commit.c
index 189d8fe..2e35992 100644
--- a/src/commit.c
+++ b/src/commit.c
@@ -129,7 +129,7 @@ int git_commit_create(
 	git_buf_puts(&commit, message);
 
 	if (git_buf_oom(&commit)) {
-		error = git__throw(git_buf_lasterror(&commit),
+		error = git__throw(GIT_ENOMEM,
 			"Not enough memory to build the commit data");
 		goto cleanup;
 	}
diff --git a/src/crlf.c b/src/crlf.c
index f0ec7b7..536b50f 100644
--- a/src/crlf.c
+++ b/src/crlf.c
@@ -128,8 +128,7 @@ static int drop_crlf(git_buf *dest, const git_buf *source)
 
 	/* Copy remaining input into dest */
 	git_buf_put(dest, scan, scan_end - scan);
-
-	return git_buf_lasterror(dest);
+	return 0;
 }
 
 static int crlf_apply_to_odb(git_filter *self, git_buf *dest, const git_buf *source)
diff --git a/src/diff_output.c b/src/diff_output.c
index 5e7486a..9c34dcf 100644
--- a/src/diff_output.c
+++ b/src/diff_output.c
@@ -482,8 +482,8 @@ static int print_compact(void *data, git_diff_delta *delta, float progress)
 	else
 		git_buf_printf(pi->buf, "%c\t%s\n", code, delta->old.path);
 
-	if (git_buf_lasterror(pi->buf) != GIT_SUCCESS)
-		return git_buf_lasterror(pi->buf);
+	if (git_buf_oom(pi->buf) == true)
+		return GIT_ENOMEM;
 
 	return pi->print_cb(pi->cb_data, GIT_DIFF_LINE_FILE_HDR, pi->buf->ptr);
 }
@@ -534,7 +534,10 @@ static int print_oid_range(diff_print_info *pi, git_diff_delta *delta)
 		git_buf_printf(pi->buf, "index %s..%s\n", start_oid, end_oid);
 	}
 
-	return git_buf_lasterror(pi->buf);
+	if (git_buf_oom(pi->buf))
+		return GIT_ENOMEM;
+
+	return 0;
 }
 
 static int print_patch_file(void *data, git_diff_delta *delta, float progress)
@@ -567,8 +570,8 @@ static int print_patch_file(void *data, git_diff_delta *delta, float progress)
 		git_buf_printf(pi->buf, "+++ %s%s\n", newpfx, newpath);
 	}
 
-	if (git_buf_lasterror(pi->buf) != GIT_SUCCESS)
-		return git_buf_lasterror(pi->buf);
+	if (git_buf_oom(pi->buf))
+		return GIT_ENOMEM;
 
 	error = pi->print_cb(pi->cb_data, GIT_DIFF_LINE_FILE_HDR, pi->buf->ptr);
 	if (error != GIT_SUCCESS || delta->binary != 1)
@@ -578,8 +581,8 @@ static int print_patch_file(void *data, git_diff_delta *delta, float progress)
 	git_buf_printf(
 		pi->buf, "Binary files %s%s and %s%s differ\n",
 		oldpfx, oldpath, newpfx, newpath);
-	if (git_buf_lasterror(pi->buf) != GIT_SUCCESS)
-		return git_buf_lasterror(pi->buf);
+	if (git_buf_oom(pi->buf))
+		return GIT_ENOMEM;
 
 	return pi->print_cb(pi->cb_data, GIT_DIFF_LINE_BINARY, pi->buf->ptr);
 }
@@ -601,7 +604,7 @@ static int print_patch_hunk(
 	if (git_buf_printf(pi->buf, "%.*s", (int)header_len, header) == GIT_SUCCESS)
 		return pi->print_cb(pi->cb_data, GIT_DIFF_LINE_HUNK_HDR, pi->buf->ptr);
 	else
-		return git_buf_lasterror(pi->buf);
+		return GIT_ENOMEM;
 }
 
 static int print_patch_line(
@@ -624,8 +627,8 @@ static int print_patch_line(
 	else if (content_len > 0)
 		git_buf_printf(pi->buf, "%.*s", (int)content_len, content);
 
-	if (git_buf_lasterror(pi->buf) != GIT_SUCCESS)
-		return git_buf_lasterror(pi->buf);
+	if (git_buf_oom(pi->buf))
+		return GIT_ENOMEM;
 
 	return pi->print_cb(pi->cb_data, line_origin, pi->buf->ptr);
 }
diff --git a/src/fileops.c b/src/fileops.c
index ffaf831..4414c86 100644
--- a/src/fileops.c
+++ b/src/fileops.c
@@ -211,20 +211,21 @@ void git_futils_mmap_free(git_map *out)
 
 int git_futils_mkdir_r(const char *path, const char *base, const mode_t mode)
 {
-	int error, root_path_offset;
+	int root_path_offset;
 	git_buf make_path = GIT_BUF_INIT;
 	size_t start;
 	char *pp, *sp;
+	bool failed = false;
 
 	if (base != NULL) {
 		start = strlen(base);
-		error = git_buf_joinpath(&make_path, base, path);
+		if (git_buf_joinpath(&make_path, base, path) < 0)
+			return -1;
 	} else {
 		start = 0;
-		error = git_buf_puts(&make_path, path);
+		if (git_buf_puts(&make_path, path) < 0)
+			return -1;
 	}
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to create `%s` tree structure", path);
 
 	pp = make_path.ptr + start;
 
@@ -232,14 +233,13 @@ int git_futils_mkdir_r(const char *path, const char *base, const mode_t mode)
 	if (root_path_offset > 0)
 		pp += root_path_offset; /* On Windows, will skip the drive name (eg. C: or D:) */
 
-	while (error == GIT_SUCCESS && (sp = strchr(pp, '/')) != NULL) {
+	while (!failed && (sp = strchr(pp, '/')) != NULL) {
 		if (sp != pp && git_path_isdir(make_path.ptr) == false) {
 			*sp = 0;
-			error = p_mkdir(make_path.ptr, mode);
 
 			/* Do not choke while trying to recreate an existing directory */
-			if (errno == EEXIST)
-				error = GIT_SUCCESS;
+			if (p_mkdir(make_path.ptr, mode) < 0 && errno != EEXIST)
+				failed = true;
 
 			*sp = '/';
 		}
@@ -247,18 +247,20 @@ int git_futils_mkdir_r(const char *path, const char *base, const mode_t mode)
 		pp = sp + 1;
 	}
 
-	if (*pp != '\0' && error == GIT_SUCCESS) {
-		error = p_mkdir(make_path.ptr, mode);
-		if (errno == EEXIST)
-			error = GIT_SUCCESS;
+	if (*pp != '\0' && !failed) {
+		if (p_mkdir(make_path.ptr, mode) < 0 && errno != EEXIST)
+			failed = true;
 	}
 
 	git_buf_free(&make_path);
 
-	if (error < GIT_SUCCESS)
-		return git__throw(error, "Failed to recursively create `%s` tree structure", path);
+	if (failed) {
+		giterr_set(GITERR_OS,
+			"Failed to create directory structure at '%s'", path);
+		return -1;
+	}
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int _rmdir_recurs_foreach(void *opaque, git_buf *path)
@@ -407,8 +409,8 @@ cleanup:
 
 int git_futils_find_system_file(git_buf *path, const char *filename)
 {
-	if (git_buf_joinpath(path, "/etc", filename) < GIT_SUCCESS)
-		return git_buf_lasterror(path);
+	if (git_buf_joinpath(path, "/etc", filename) < 0)
+		return -1;
 
 	if (git_path_exists(path->ptr) == true)
 		return GIT_SUCCESS;
diff --git a/src/indexer.c b/src/indexer.c
index de1e5dc..dd7c719 100644
--- a/src/indexer.c
+++ b/src/indexer.c
@@ -171,7 +171,10 @@ static int index_path(git_buf *path, git_indexer *idx)
 	path->size += GIT_OID_HEXSZ;
 	git_buf_puts(path, suffix);
 
-	return git_buf_lasterror(path);
+	if (git_buf_oom(path))
+		return GIT_ENOMEM;
+
+	return 0;
 }
 
 int git_indexer_write(git_indexer *idx)
@@ -192,8 +195,8 @@ int git_indexer_write(git_indexer *idx)
 	git_buf_truncate(&filename, filename.size - strlen("pack"));
 	git_buf_puts(&filename, "idx");
 
-	if ((error = git_buf_lasterror(&filename)) < GIT_SUCCESS)
-		goto cleanup;
+	if (git_buf_oom(&filename))
+		return GIT_ENOMEM;
 
 	error = git_filebuf_open(&idx->file, filename.ptr, GIT_FILEBUF_HASH_CONTENTS);
 	if (error < GIT_SUCCESS)
diff --git a/src/odb_loose.c b/src/odb_loose.c
index 2dd7004..17fede4 100644
--- a/src/odb_loose.c
+++ b/src/odb_loose.c
@@ -387,8 +387,8 @@ static int read_loose(git_rawobj *out, git_buf *loc)
 
 	assert(out && loc);
 
-	if ((error = git_buf_lasterror(loc)) < GIT_SUCCESS)
-		return error;
+	if (git_buf_oom(loc))
+		return GIT_ENOMEM;
 
 	out->data = NULL;
 	out->len = 0;
@@ -413,8 +413,8 @@ static int read_header_loose(git_rawobj *out, git_buf *loc)
 
 	assert(out && loc);
 
-	if ((error = git_buf_lasterror(loc)) < GIT_SUCCESS)
-		return error;
+	if (git_buf_oom(loc))
+		return GIT_ENOMEM;
 
 	out->data = NULL;
 
@@ -704,8 +704,8 @@ static int loose_backend__stream_fwrite(git_oid *oid, git_odb_stream *_stream)
 	if ((error = object_file_name(&final_path, backend->objects_dir, oid)) < GIT_SUCCESS)
 		goto cleanup;
 
-	if ((error = git_buf_lasterror(&final_path)) < GIT_SUCCESS)
-		goto cleanup;
+	if (git_buf_oom(&final_path))
+		return GIT_ENOMEM;
 
 	if ((error = git_futils_mkpath2file(final_path.ptr, GIT_OBJECT_DIR_MODE)) < GIT_SUCCESS)
 		goto cleanup;
diff --git a/src/path.c b/src/path.c
index 5d35e0e..8d0cf28 100644
--- a/src/path.c
+++ b/src/path.c
@@ -56,7 +56,7 @@ Exit:
 
 	if (buffer != NULL) {
 		if (git_buf_set(buffer, startp, len) < GIT_SUCCESS)
-			return git__rethrow(git_buf_lasterror(buffer),
+			return git__rethrow(GIT_ENOMEM,
 				"Could not get basename of '%s'", path);
 	}
 
@@ -116,7 +116,7 @@ Exit:
 
 	if (buffer != NULL) {
 		if (git_buf_set(buffer, path, len) < GIT_SUCCESS)
-			return git__rethrow(git_buf_lasterror(buffer),
+			return git__rethrow(GIT_ENOMEM,
 				"Could not get dirname of '%s'", path);
 	}
 
@@ -185,34 +185,36 @@ int git_path_root(const char *path)
 
 int git_path_prettify(git_buf *path_out, const char *path, const char *base)
 {
-	int  error = GIT_SUCCESS;
 	char buf[GIT_PATH_MAX];
 
+	assert(path && path_out);
 	git_buf_clear(path_out);
 
 	/* construct path if needed */
 	if (base != NULL && git_path_root(path) < 0) {
-		if ((error = git_buf_joinpath(path_out, base, path)) < GIT_SUCCESS)
-			return error;
+		if (git_buf_joinpath(path_out, base, path) < 0)
+			return -1;
+
 		path = path_out->ptr;
 	}
 
-	if (path == NULL || p_realpath(path, buf) == NULL)
-		error = GIT_EOSERR;
-	else
-		error = git_buf_sets(path_out, buf);
+	if (p_realpath(path, buf) == NULL) {
+		giterr_set(GITERR_OS, "Failed to resolve path '%s': %s", path, strerror(errno));
+		return (errno == ENOENT) ? GIT_ENOTFOUND : -1;
+	}
 
-	return error;
+	if (git_buf_sets(path_out, buf) < 0)
+		return -1;
+
+	return 0;
 }
 
 int git_path_prettify_dir(git_buf *path_out, const char *path, const char *base)
 {
-	int error = git_path_prettify(path_out, path, base);
-
-	if (error == GIT_SUCCESS)
-		error = git_path_to_dir(path_out);
+	if (git_path_prettify(path_out, path, base) < 0)
+		return -1;
 
-	return error;
+	return git_path_to_dir(path_out);
 }
 
 int git_path_to_dir(git_buf *path)
@@ -222,7 +224,10 @@ int git_path_to_dir(git_buf *path)
 		path->ptr[path->size - 1] != '/')
 		git_buf_putc(path, '/');
 
-	return git_buf_lasterror(path);
+	if (git_buf_oom(path))
+		return -1;
+
+	return 0;
 }
 
 void git_path_string_to_dir(char* path, size_t size)
@@ -445,7 +450,7 @@ int git_path_find_dir(git_buf *dir, const char *path, const char *base)
 	/* call dirname if this is not a directory */
 	if (error == GIT_SUCCESS && git_path_isdir(dir->ptr) == false)
 		if (git_path_dirname_r(dir, dir->ptr) < GIT_SUCCESS)
-			error = git_buf_lasterror(dir);
+			error = GIT_ENOMEM;
 
 	if (error == GIT_SUCCESS)
 		error = git_path_to_dir(dir);
diff --git a/src/reflog.c b/src/reflog.c
index 8f68a3a..5352760 100644
--- a/src/reflog.c
+++ b/src/reflog.c
@@ -65,9 +65,9 @@ static int reflog_write(const char *log_path, const char *oid_old,
 
 	git_buf_putc(&log, '\n');
 
-	if ((error = git_buf_lasterror(&log)) < GIT_SUCCESS) {
+	if (git_buf_oom(&log)) {
 		git_buf_free(&log);
-		return git__rethrow(error, "Failed to write reflog. Memory allocation failure");
+		return git__throw(GIT_ENOMEM, "Failed to write reflog. Memory allocation failure");
 	}
 
 	if ((error = git_filebuf_open(&fbuf, log_path, GIT_FILEBUF_APPEND)) < GIT_SUCCESS) {
diff --git a/src/refspec.c b/src/refspec.c
index a271414..d51fd4c 100644
--- a/src/refspec.c
+++ b/src/refspec.c
@@ -97,7 +97,7 @@ int git_refspec_transform(char *out, size_t outlen, const git_refspec *spec, con
 int git_refspec_transform_r(git_buf *out, const git_refspec *spec, const char *name)
 {
 	if (git_buf_sets(out, spec->dst) < GIT_SUCCESS)
-		return git_buf_lasterror(out);
+		return GIT_ENOMEM;
 
 	/*
 	 * No '*' at the end means that it's mapped to one specific local
@@ -109,5 +109,9 @@ int git_refspec_transform_r(git_buf *out, const git_refspec *spec, const char *n
 	git_buf_truncate(out, out->size - 1); /* remove trailing '*' */
 	git_buf_puts(out, name + strlen(spec->src) - 1);
 
-	return git_buf_lasterror(out);
+	if (git_buf_oom(out))
+		return GIT_ENOMEM;
+
+	return 0;
 }
+
diff --git a/src/repository.c b/src/repository.c
index e274252..7d7b3c4 100644
--- a/src/repository.c
+++ b/src/repository.c
@@ -80,35 +80,31 @@ void git_repository_free(git_repository *repo)
  *
  * Open a repository object from its path
  */
-static int quickcheck_repository_dir(git_buf *repository_path)
+static bool valid_repository_path(git_buf *repository_path)
 {
 	/* Check OBJECTS_DIR first, since it will generate the longest path name */
 	if (git_path_contains_dir(repository_path, GIT_OBJECTS_DIR) == false)
-		return GIT_ERROR;
+		return false;
 
 	/* Ensure HEAD file exists */
 	if (git_path_contains_file(repository_path, GIT_HEAD_FILE) == false)
-		return GIT_ERROR;
+		return false;
 
 	if (git_path_contains_dir(repository_path, GIT_REFS_DIR)  == false)
-		return GIT_ERROR;
+		return false;
 
-	return GIT_SUCCESS;
+	return true;
 }
 
-
 static git_repository *repository_alloc(void)
 {
-	int error;
-
 	git_repository *repo = git__malloc(sizeof(git_repository));
 	if (!repo)
 		return NULL;
 
 	memset(repo, 0x0, sizeof(git_repository));
 
-	error = git_cache_init(&repo->objects, GIT_DEFAULT_CACHE_SIZE, &git_object__free);
-	if (error < GIT_SUCCESS) {
+	if (git_cache_init(&repo->objects, GIT_DEFAULT_CACHE_SIZE, &git_object__free) < 0) {
 		git__free(repo);
 		return NULL;
 	}
@@ -121,50 +117,48 @@ static git_repository *repository_alloc(void)
 
 static int load_config_data(git_repository *repo)
 {
-	int error, is_bare;
+	int is_bare;
 	git_config *config;
 
-	error = git_repository_config__weakptr(&config, repo);
-	if (error < GIT_SUCCESS)
-		return error;
-
-	error = git_config_get_bool(config, "core.bare", &is_bare);
-	if (error == GIT_SUCCESS)
-		repo->is_bare = is_bare;
+	if (git_repository_config__weakptr(&config, repo) < 0)
+		return -1;
 
-	/* TODO: what else can we load/cache here? */
+	if (git_config_get_bool(config, "core.bare", &is_bare) < 0)
+		return -1; /* FIXME: We assume that a missing core.bare
+					  variable is an error. Is this right? */
 
-	return GIT_SUCCESS;
+	repo->is_bare = is_bare;
+	return 0;
 }
 
 static int load_workdir(git_repository *repo)
 {
-	int error;
 	git_buf workdir_buf = GIT_BUF_INIT;
 
 	if (repo->is_bare)
-		return GIT_SUCCESS;
+		return 0;
 
 	git_path_dirname_r(&workdir_buf, repo->path_repository);
 	git_path_to_dir(&workdir_buf);
 
-	if ((error = git_buf_lasterror(&workdir_buf)) == GIT_SUCCESS)
-		repo->workdir = git_buf_detach(&workdir_buf);
+	if (git_buf_oom(&workdir_buf))
+		return -1;
 
+	repo->workdir = git_buf_detach(&workdir_buf);
 	git_buf_free(&workdir_buf);
 
-	return error;
+	return 0;
 }
 
 int git_repository_open(git_repository **repo_out, const char *path)
 {
-	int error = GIT_SUCCESS;
 	git_buf path_buf = GIT_BUF_INIT;
 	git_repository *repo = NULL;
+	int res;
 
-	error = git_path_prettify_dir(&path_buf, path, NULL);
-	if (error < GIT_SUCCESS)
-		goto cleanup;
+	res = git_path_prettify_dir(&path_buf, path, NULL);
+	if (res < 0)
+		return res;
 
 	/**
 	 * Check if the path we've been given is actually the path
@@ -174,39 +168,32 @@ int git_repository_open(git_repository **repo_out, const char *path)
 	if (git_path_contains_dir(&path_buf, GIT_DIR) == true)
 		git_buf_joinpath(&path_buf, path_buf.ptr, GIT_DIR);
 
-	if (quickcheck_repository_dir(&path_buf) < GIT_SUCCESS) {
-		error = git__throw(GIT_ENOTAREPO,
+	if (valid_repository_path(&path_buf) == false) {
+		giterr_set(GITERR_REPOSITORY,
 			"The given path (%s) is not a valid Git repository", git_buf_cstr(&path_buf));
-		goto cleanup;
+		git_buf_free(&path_buf);
+		return GIT_ENOTFOUND;
 	}
 
 	repo = repository_alloc();
-	if (repo == NULL) {
-		error = GIT_ENOMEM;
-		goto cleanup;
-	}
+	GITERR_CHECK_ALLOC(repo);
 
 	repo->path_repository = git_buf_detach(&path_buf);
-	if (repo->path_repository == NULL) {
-		error = GIT_ENOMEM;
-		goto cleanup;
-	}
+	GITERR_CHECK_ALLOC(repo->path_repository);
 
-	error = load_config_data(repo);
-	if (error < GIT_SUCCESS)
+	if (load_config_data(repo) < 0)
 		goto cleanup;
 
-	error = load_workdir(repo);
-	if (error < GIT_SUCCESS)
+	if (load_workdir(repo) < 0)
 		goto cleanup;
 
 	*repo_out = repo;
-	return GIT_SUCCESS;
+	return 0;
 
  cleanup:
 	git_repository_free(repo);
 	git_buf_free(&path_buf);
-	return error;
+	return -1;
 }
 
 static int load_config(
@@ -216,85 +203,79 @@ static int load_config(
 		const char *system_config_path)
 {
 	git_buf config_path = GIT_BUF_INIT;
-	int error;
 	git_config *cfg = NULL;
 
 	assert(repo && out);
 
-	error = git_config_new(&cfg);
-	if (error < GIT_SUCCESS)
-		return error;
+	if (git_config_new(&cfg) < 0)
+		return -1;
 
-	error = git_buf_joinpath(&config_path, repo->path_repository,
-							 GIT_CONFIG_FILENAME_INREPO);
-	if (error < GIT_SUCCESS)
-		goto cleanup;
+	if (git_buf_joinpath(
+		&config_path, repo->path_repository, GIT_CONFIG_FILENAME_INREPO) < 0)
+		goto on_error;
 
-	error = git_config_add_file_ondisk(cfg, config_path.ptr, 3);
-	git_buf_free(&config_path); /* done with config_path now */
-	if (error < GIT_SUCCESS)
-		goto cleanup;
+	if (git_config_add_file_ondisk(cfg, config_path.ptr, 3) < 0)
+		goto on_error;
+
+	git_buf_free(&config_path);
 
 	if (global_config_path != NULL) {
-		error = git_config_add_file_ondisk(cfg, global_config_path, 2);
-		if (error < GIT_SUCCESS)
-			goto cleanup;
+		if (git_config_add_file_ondisk(cfg, global_config_path, 2) < 0)
+			goto on_error;
 	}
 
 	if (system_config_path != NULL) {
-		error = git_config_add_file_ondisk(cfg, system_config_path, 1);
-		if (error < GIT_SUCCESS)
-			goto cleanup;
+		if (git_config_add_file_ondisk(cfg, system_config_path, 1) < 0)
+			goto on_error;
 	}
 
 	*out = cfg;
-	return GIT_SUCCESS;
+	return 0;
 
-cleanup:
+on_error:
+	git_buf_free(&config_path);
 	git_config_free(cfg);
 	*out = NULL;
-	return error;
+	return -1;
 }
 
 int git_repository_config__weakptr(git_config **out, git_repository *repo)
 {
 	if (repo->_config == NULL) {
-		int error;
 		git_buf global_buf = GIT_BUF_INIT, system_buf = GIT_BUF_INIT;
+		int res;
 
 		const char *global_config_path = NULL;
 		const char *system_config_path = NULL;
 
-		if (git_config_find_global_r(&global_buf) == GIT_SUCCESS)
+		if (git_config_find_global_r(&global_buf) == 0)
 			global_config_path = global_buf.ptr;
 
-		if (git_config_find_system_r(&system_buf) == GIT_SUCCESS)
+		if (git_config_find_system_r(&system_buf) == 0)
 			system_config_path = system_buf.ptr;
 
-		error = load_config(&repo->_config, repo, global_config_path, system_config_path);
+		res = load_config(&repo->_config, repo, global_config_path, system_config_path);
 
 		git_buf_free(&global_buf);
 		git_buf_free(&system_buf);
 
-		if (error < GIT_SUCCESS)
-			return error;
+		if (res < 0)
+			return -1;
 
 		GIT_REFCOUNT_OWN(repo->_config, repo);
 	}
 
 	*out = repo->_config;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_repository_config(git_config **out, git_repository *repo)
 {
-	int error = git_repository_config__weakptr(out, repo);
-
-	if (error == GIT_SUCCESS) {
-		GIT_REFCOUNT_INC(*out);
-	}
+	if (git_repository_config__weakptr(out, repo) < 0)
+		return -1;
 
-	return error;
+	GIT_REFCOUNT_INC(*out);
+	return 0;
 }
 
 void git_repository_set_config(git_repository *repo, git_config *config)
@@ -312,34 +293,32 @@ int git_repository_odb__weakptr(git_odb **out, git_repository *repo)
 	assert(repo && out);
 
 	if (repo->_odb == NULL) {
-		int error;
 		git_buf odb_path = GIT_BUF_INIT;
+		int res;
 
-		error = git_buf_joinpath(&odb_path, repo->path_repository, GIT_OBJECTS_DIR);
-		if (error < GIT_SUCCESS)
-			return error;
+		if (git_buf_joinpath(&odb_path, repo->path_repository, GIT_OBJECTS_DIR) < 0)
+			return -1;
 
-		error = git_odb_open(&repo->_odb, odb_path.ptr);
+		res = git_odb_open(&repo->_odb, odb_path.ptr);
 		git_buf_free(&odb_path); /* done with path */
-		if (error < GIT_SUCCESS)
-			return error;
+
+		if (res < 0)
+			return -1;
 
 		GIT_REFCOUNT_OWN(repo->_odb, repo);
 	}
 
 	*out = repo->_odb;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_repository_odb(git_odb **out, git_repository *repo)
 {
-	int error = git_repository_odb__weakptr(out, repo);
+	if (git_repository_odb__weakptr(out, repo) < 0)
+		return -1;
 
-	if (error == GIT_SUCCESS) {
-		GIT_REFCOUNT_INC(*out);
-	}
-
-	return error;
+	GIT_REFCOUNT_INC(*out);
+	return 0;
 }
 
 void git_repository_set_odb(git_repository *repo, git_odb *odb)
@@ -357,34 +336,32 @@ int git_repository_index__weakptr(git_index **out, git_repository *repo)
 	assert(out && repo);
 
 	if (repo->_index == NULL) {
-		int error;
+		int res;
 		git_buf index_path = GIT_BUF_INIT;
 
-		error = git_buf_joinpath(&index_path, repo->path_repository, GIT_INDEX_FILE);
-		if (error < GIT_SUCCESS)
-			return error;
+		if (git_buf_joinpath(&index_path, repo->path_repository, GIT_INDEX_FILE) < 0)
+			return -1;
 
-		error = git_index_open(&repo->_index, index_path.ptr);
+		res = git_index_open(&repo->_index, index_path.ptr);
 		git_buf_free(&index_path); /* done with path */
-		if (error < GIT_SUCCESS)
-			return error;
+
+		if (res < 0)
+			return -1;
 
 		GIT_REFCOUNT_OWN(repo->_index, repo);
 	}
 
 	*out = repo->_index;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_repository_index(git_index **out, git_repository *repo)
 {
-	int error = git_repository_index__weakptr(out, repo);
+	if (git_repository_index__weakptr(out, repo) < 0)
+		return -1;
 
-	if (error == GIT_SUCCESS) {
-		GIT_REFCOUNT_INC(*out);
-	}
-
-	return error;
+	GIT_REFCOUNT_INC(*out);
+	return 0;
 }
 
 void git_repository_set_index(git_repository *repo, git_index *index)
@@ -404,12 +381,13 @@ static int retrieve_device(dev_t *device_out, const char *path)
 
 	assert(device_out);
 
-	if (p_lstat(path, &path_info))
-		return git__throw(GIT_EOSERR, "Failed to get file informations: %s", path);
+	if (p_lstat(path, &path_info)) {
+		giterr_set(GITERR_OS, "Failed to retrieve file information: %s", strerror(errno));
+		return -1;
+	}
 
 	*device_out = path_info.st_dev;
-
-	return GIT_SUCCESS;
+	return 0;
 }
 
 /*
@@ -473,35 +451,31 @@ static int retrieve_ceiling_directories_offset(
 static int read_gitfile(git_buf *path_out, const char *file_path, const char *base_path)
 {
 	git_buf file = GIT_BUF_INIT;
-	int error;
 
 	assert(path_out && file_path);
 
-	error = git_futils_readbuffer(&file, file_path);
-	if (error < GIT_SUCCESS)
-		return error;
-
-	if (git__prefixcmp((char *)file.ptr, GIT_FILE_CONTENT_PREFIX)) {
-		git_buf_free(&file);
-		return git__throw(GIT_ENOTFOUND, "Invalid gitfile format `%s`", file_path);
-	}
+	if (git_futils_readbuffer(&file, file_path) < 0)
+		return -1;
 
 	git_buf_rtrim(&file);
 
-	if (strlen(GIT_FILE_CONTENT_PREFIX) == file.size) {
+	if (git__prefixcmp((char *)file.ptr, GIT_FILE_CONTENT_PREFIX) != 0 ||
+		strlen(GIT_FILE_CONTENT_PREFIX) == file.size) {
 		git_buf_free(&file);
-		return git__throw(GIT_ENOTFOUND, "No path in git file `%s`", file_path);
+		giterr_set(GITERR_REPOSITORY, "The `.git` file at '%s' is corrupted", file_path);
+		return -1;
 	}
 
-	error = git_path_prettify_dir(path_out,
-		((char *)file.ptr) + strlen(GIT_FILE_CONTENT_PREFIX), base_path);
+	if (git_path_prettify_dir(path_out,
+		((char *)file.ptr) + strlen(GIT_FILE_CONTENT_PREFIX), base_path) < 0) {
+		git_buf_free(&file);
+		giterr_set(GITERR_REPOSITORY,
+			"The `.git` file at '%s' points to an invalid path.", file_path);
+		return -1;
+	}
 
 	git_buf_free(&file);
-
-	if (error == GIT_SUCCESS && git_path_exists(path_out->ptr) == true)
-		return GIT_SUCCESS;
-
-	return git__throw(GIT_EOBJCORRUPTED, "The `.git` file points to a nonexistent path");
+	return 0;
 }
 
 int git_repository_discover(
@@ -511,7 +485,7 @@ int git_repository_discover(
 	int across_fs,
 	const char *ceiling_dirs)
 {
-	int error, ceiling_offset;
+	int res, ceiling_offset;
 	git_buf bare_path = GIT_BUF_INIT;
 	git_buf normal_path = GIT_BUF_INIT;
 	git_buf *found_path = NULL;
@@ -521,22 +495,20 @@ int git_repository_discover(
 
 	*repository_path = '\0';
 
-	error = git_path_prettify_dir(&bare_path, start_path, NULL);
-	if (error < GIT_SUCCESS)
-		goto cleanup;
+	res = git_path_prettify_dir(&bare_path, start_path, NULL);
+	if (res < 0)
+		return res;
 
 	if (!across_fs) {
-		error = retrieve_device(&current_device, bare_path.ptr);
-		if (error < GIT_SUCCESS)
-			goto cleanup;
+		if (retrieve_device(&current_device, bare_path.ptr) < 0)
+			goto on_error;
 	}
 
 	ceiling_offset = retrieve_ceiling_directories_offset(bare_path.ptr, ceiling_dirs);
 
 	while(1) {
-		error = git_buf_joinpath(&normal_path, bare_path.ptr, DOT_GIT);
-		if (error < GIT_SUCCESS)
-			break;
+		if (git_buf_joinpath(&normal_path, bare_path.ptr, DOT_GIT) < 0)
+			goto on_error;
 
 		/**
 		 * If the `.git` file is regular instead of
@@ -545,18 +517,21 @@ int git_repository_discover(
 		if (git_path_isfile(normal_path.ptr) == true) {
 			git_buf gitfile_path = GIT_BUF_INIT;
 
-			error = read_gitfile(&gitfile_path, normal_path.ptr, bare_path.ptr);
-			if (error < GIT_SUCCESS)
-				git__rethrow(error, "Unable to read git file `%s`", normal_path.ptr);
-			else if ((error = quickcheck_repository_dir(&gitfile_path)) < GIT_SUCCESS)
-				git__throw(GIT_ENOTFOUND,
-					"The `.git` file found at '%s' points "
-					"to a nonexistent git folder", normal_path.ptr);
-			else {
-				git_buf_swap(&normal_path, &gitfile_path);
-				found_path = &normal_path;
+			if (read_gitfile(&gitfile_path, normal_path.ptr, bare_path.ptr) < 0) {
+				git_buf_free(&gitfile_path);
+				goto on_error;
 			}
 
+			if (valid_repository_path(&gitfile_path) == false) {
+				git_buf_free(&gitfile_path);
+				giterr_set(GITERR_REPOSITORY,
+					"The `.git` file found at '%s' points to an invalid git folder", normal_path.ptr);
+				goto on_error;
+			}
+
+			git_buf_swap(&normal_path, &gitfile_path);
+			found_path = &normal_path;
+
 			git_buf_free(&gitfile_path);
 			break;
 		}
@@ -565,8 +540,7 @@ int git_repository_discover(
 		 * If the `.git` file is a folder, we check inside of it
 		 */
 		if (git_path_isdir(normal_path.ptr) == true) {
-			error = quickcheck_repository_dir(&normal_path);
-			if (error == GIT_SUCCESS) {
+			if (valid_repository_path(&normal_path) == true) {
 				found_path = &normal_path;
 				break;
 			}
@@ -576,8 +550,7 @@ int git_repository_discover(
 		 * Otherwise, the repository may be bare, let's check
 		 * the root anyway
 		 */
-		error = quickcheck_repository_dir(&bare_path);
-		if (error == GIT_SUCCESS) {
+		if (valid_repository_path(&bare_path) == true) {
 			found_path = &bare_path;
 			break;
 		}
@@ -585,147 +558,146 @@ int git_repository_discover(
 		/**
 		 * If we didn't find it, walk up the tree
 		 */
-		error = git_path_dirname_r(&normal_path, bare_path.ptr);
-		if (error < GIT_SUCCESS) {
-			git__rethrow(GIT_EOSERR, "Failed to dirname '%s'", bare_path.ptr);
-			break;
-		}
+		if (git_path_dirname_r(&normal_path, bare_path.ptr) < 0)
+			goto on_error;
 
 		git_buf_swap(&bare_path, &normal_path);
 
 		if (!across_fs) {
 			dev_t new_device;
-			error = retrieve_device(&new_device, bare_path.ptr);
+			if (retrieve_device(&new_device, bare_path.ptr) < 0)
+				goto on_error;
+
+			if (current_device != new_device)
+				goto on_not_found;
 
-			if (error < GIT_SUCCESS || current_device != new_device) {
-				error = git__throw(GIT_ENOTAREPO,
-					"Not a git repository (or any parent up to mount parent %s)\n"
-					"Stopping at filesystem boundary.", normal_path.ptr);
-				break;
-			}
 			current_device = new_device;
 		}
 
 		/* nothing has been found, lets try the parent directory
 		 * but stop if we hit one of the ceiling directories
 		 */
-		if (bare_path.ptr[ceiling_offset] == '\0') {
-			error = git__throw(GIT_ENOTAREPO,
-				"Not a git repository (or any of the parent directories): %s", start_path);
-			break;
-		}
+		if (bare_path.ptr[ceiling_offset] == '\0')
+			goto on_not_found;
 	}
 
-	assert(found_path || error != GIT_SUCCESS);
-
-	if (found_path) {
-		if ((error = git_path_to_dir(found_path)) < GIT_SUCCESS)
-			git__rethrow(error, "Could not convert git repository to directory");
-		else if (size < (size_t)(found_path->size + 1))
-			error = git__throw(GIT_ESHORTBUFFER,
-				"The repository buffer is not long enough to "
-				"handle the repository path `%s`", found_path->ptr);
-		else
-			git_buf_copy_cstr(repository_path, size, found_path);
+	assert(found_path);
+
+	if (git_path_to_dir(found_path) < 0)
+		goto on_error;
+
+	if (size < (size_t)(found_path->size + 1)) {
+		giterr_set(GITERR_REPOSITORY,
+			"The given buffer is too long to store the discovered path");
+		goto on_error;
 	}
 
-cleanup:
+	/* success: we discovered a repository */
+	git_buf_copy_cstr(repository_path, size, found_path);
+
+	git_buf_free(&bare_path);
+	git_buf_free(&normal_path);
+	return 0;
+
+on_error: /* unrecoverable error */
 	git_buf_free(&bare_path);
 	git_buf_free(&normal_path);
-	return error;
+	return -1;
+
+on_not_found: /* failed to discover the repository */
+	git_buf_free(&bare_path);
+	git_buf_free(&normal_path);
+	return GIT_ENOTFOUND;
 }
 
 static int check_repositoryformatversion(git_repository *repo)
 {
 	git_config *config;
-	int version, error = GIT_SUCCESS;
-
-	if ((error = git_repository_config(&config, repo)) < GIT_SUCCESS)
-		return git__throw(error, "Failed to open config file.");
+	int version;
 
-	error = git_config_get_int32(config, GIT_CONFIG_CORE_REPOSITORYFORMATVERSION, &version);
+	if (git_repository_config__weakptr(&config, repo) < 0)
+		return -1;
 
-	if (GIT_REPOSITORYFORMATVERSION < version)
-		error = git__throw(GIT_ERROR, "Unsupported git repository version (Expected version <= %d, found %d).", GIT_REPOSITORYFORMATVERSION, version);
+	if (git_config_get_int32(config, GIT_CONFIG_CORE_REPOSITORYFORMATVERSION, &version) < 0)
+		return -1;
 
-	git_config_free(config);
+	if (GIT_REPOSITORYFORMATVERSION < version) {
+		giterr_set(GITERR_REPOSITORY,
+			"Unsupported repository version %d. Only versions up to %d are supported.",
+			version, GIT_REPOSITORYFORMATVERSION);
+		return -1;
+	}
 
-	return error;
+	return 0;
 }
 
 static int repo_init_reinit(git_repository **repo_out, const char *repository_path, int is_bare)
 {
-	int error;
 	git_repository *repo = NULL;
 
-	if ((error = git_repository_open(&repo, repository_path)) < GIT_SUCCESS)
-		goto error;
+	GIT_UNUSED(is_bare);
 
-	if ((error = check_repositoryformatversion(repo)) < GIT_SUCCESS)
-		goto error;
+	if (git_repository_open(&repo, repository_path) < 0)
+		return -1;
+
+	if (check_repositoryformatversion(repo) < 0) {
+		git_repository_free(repo);
+		return -1;
+	}
 
 	/* TODO: reinitialize the templates */
 
 	*repo_out = repo;
-
-	return GIT_SUCCESS;
-
-error:
-	git_repository_free(repo);
-
-	return git__rethrow(error,
-		"Failed to reinitialize the %srepository at '%s'. ",
-		is_bare ? "bare " : "", repository_path);
+	return 0;
 }
 
 static int repo_init_createhead(const char *git_dir)
 {
-	int error;
 	git_buf ref_path = GIT_BUF_INIT;
 	git_filebuf ref = GIT_FILEBUF_INIT;
 
-	if (!(error = git_buf_joinpath(&ref_path, git_dir, GIT_HEAD_FILE)) &&
-		!(error = git_filebuf_open(&ref, ref_path.ptr, 0)) &&
-		!(error = git_filebuf_printf(&ref, "ref: refs/heads/master\n")))
-		error = git_filebuf_commit(&ref, GIT_REFS_FILE_MODE);
+	if (git_buf_joinpath(&ref_path, git_dir, GIT_HEAD_FILE) < 0 ||
+		git_filebuf_open(&ref, ref_path.ptr, 0) < 0 ||
+		git_filebuf_printf(&ref, "ref: refs/heads/master\n") < 0 ||
+		git_filebuf_commit(&ref, GIT_REFS_FILE_MODE) < 0)
+		return -1;
 
 	git_buf_free(&ref_path);
-	return error;
+	return 0;
 }
 
 static int repo_init_config(const char *git_dir, int is_bare)
 {
 	git_buf cfg_path = GIT_BUF_INIT;
 	git_config *config = NULL;
-	int error = GIT_SUCCESS;
 
 #define SET_REPO_CONFIG(type, name, val) {\
-	error = git_config_set_##type(config, name, val);\
-	if (error < GIT_SUCCESS)\
-		goto cleanup;\
+	if (git_config_set_##type(config, name, val) < 0) { \
+		git_buf_free(&cfg_path); \
+		git_config_free(config); \
+		return -1; } \
 }
 
-	error = git_buf_joinpath(&cfg_path, git_dir, GIT_CONFIG_FILENAME_INREPO);
-	if (error < GIT_SUCCESS)
-		goto cleanup;
+	if (git_buf_joinpath(&cfg_path, git_dir, GIT_CONFIG_FILENAME_INREPO) < 0)
+		return -1;
 
-	error = git_config_open_ondisk(&config, cfg_path.ptr);
-	if (error < GIT_SUCCESS)
-		goto cleanup;
+	if (git_config_open_ondisk(&config, cfg_path.ptr) < 0) {
+		git_buf_free(&cfg_path);
+		return -1;
+	}
 
 	SET_REPO_CONFIG(bool, "core.bare", is_bare);
 	SET_REPO_CONFIG(int32, GIT_CONFIG_CORE_REPOSITORYFORMATVERSION, GIT_REPOSITORYFORMATVERSION);
 	/* TODO: what other defaults? */
 
-cleanup:
 	git_buf_free(&cfg_path);
 	git_config_free(config);
-	return error;
+	return 0;
 }
 
 static int repo_init_structure(const char *git_dir, int is_bare)
 {
-	int error, i;
+	int i;
 	struct { const char *dir; mode_t mode; } dirs[] = {
 		{ GIT_OBJECTS_INFO_DIR, GIT_OBJECT_DIR_MODE }, /* '/objects/info/' */
 		{ GIT_OBJECTS_PACK_DIR, GIT_OBJECT_DIR_MODE }, /* '/objects/pack/' */
@@ -735,100 +707,80 @@ static int repo_init_structure(const char *git_dir, int is_bare)
 	};
 
 	/* Make the base directory */
-	error = git_futils_mkdir_r(git_dir, NULL, is_bare ?
-							   GIT_BARE_DIR_MODE : GIT_DIR_MODE);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to initialize repository structure. Could not mkdir");
+	if (git_futils_mkdir_r(git_dir, NULL, is_bare ? GIT_BARE_DIR_MODE : GIT_DIR_MODE) < 0)
+		return -1;
 
 	/* Hides the ".git" directory */
 	if (!is_bare) {
 #ifdef GIT_WIN32
-		error = p_hide_directory__w32(git_dir);
-		if (error < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to initialize repository structure");
+		if (p_hide_directory__w32(git_dir) < 0) {
+			giterr_set(GITERR_REPOSITORY,
+				"Failed to mark Git repository folder as hidden");
+			return -1;
+		}
 #endif
 	}
 
 	/* Make subdirectories as needed */
 	for (i = 0; dirs[i].dir != NULL; ++i) {
-		error = git_futils_mkdir_r(dirs[i].dir, git_dir, dirs[i].mode);
-		if (error < GIT_SUCCESS)
-			return git__rethrow(error,
-				"Failed to create repository folder `%s`", dirs[i].dir);
+		if (git_futils_mkdir_r(dirs[i].dir, git_dir, dirs[i].mode) < 0)
+			return -1;
 	}
 
 	/* TODO: what's left? templates? */
-
-	return error;
+	return 0;
 }
 
 int git_repository_init(git_repository **repo_out, const char *path, unsigned is_bare)
 {
-	int error = GIT_SUCCESS;
-	git_repository *repo = NULL;
 	git_buf repository_path = GIT_BUF_INIT;
 
 	assert(repo_out && path);
 
-	error = git_buf_joinpath(&repository_path, path, is_bare ? "" : GIT_DIR);
-	if (error < GIT_SUCCESS)
-		return error;
+	if (git_buf_joinpath(&repository_path, path, is_bare ? "" : GIT_DIR) < 0)
+		return -1;
 
 	if (git_path_isdir(repository_path.ptr) == true) {
-		if (quickcheck_repository_dir(&repository_path) == GIT_SUCCESS) {
-			error = repo_init_reinit(repo_out, repository_path.ptr, is_bare);
+		if (valid_repository_path(&repository_path) == true) {
+			int res = repo_init_reinit(repo_out, repository_path.ptr, is_bare);
 			git_buf_free(&repository_path);
-			return error;
+			return res;
 		}
 	}
 
-	if (!(error = repo_init_structure(repository_path.ptr, is_bare)) &&
-		!(error = repo_init_config(repository_path.ptr, is_bare)) &&
-		!(error = repo_init_createhead(repository_path.ptr)))
-		error = git_repository_open(repo_out, repository_path.ptr);
-	else
-		git_repository_free(repo);
+	if (repo_init_structure(repository_path.ptr, is_bare) < 0 ||
+		repo_init_config(repository_path.ptr, is_bare) < 0 || 
+		repo_init_createhead(repository_path.ptr) < 0 ||
+		git_repository_open(repo_out, repository_path.ptr) < 0) {
+		git_buf_free(&repository_path);
+		return -1;
+	}
 
 	git_buf_free(&repository_path);
-
-	if (error != GIT_SUCCESS)
-		git__rethrow(error, "Failed to (re)init the repository `%s`", path);
-
-	return error;
+	return 0;
 }
 
 int git_repository_head_detached(git_repository *repo)
 {
 	git_reference *ref;
-	int error;
-	size_t _size;
-	git_otype type;
 	git_odb *odb = NULL;
+	int exists;
 
-	error = git_repository_odb__weakptr(&odb, repo);
-	if (error < GIT_SUCCESS)
-		return error;
+	if (git_repository_odb__weakptr(&odb, repo) < 0)
+		return -1;
 
-	error = git_reference_lookup(&ref, repo, GIT_HEAD_FILE);
-	if (error < GIT_SUCCESS)
-		return error;
+	if (git_reference_lookup(&ref, repo, GIT_HEAD_FILE) < 0)
+		return -1;
 
 	if (git_reference_type(ref) == GIT_REF_SYMBOLIC) {
 		git_reference_free(ref);
 		return 0;
 	}
 
-	error = git_odb_read_header(&_size, &type, odb, git_reference_oid(ref));
+	exists = git_odb_exists(odb, git_reference_oid(ref));
 
 	git_reference_free(ref);
-
-	if (error < GIT_SUCCESS)
-		return error;
-
-	if (type != GIT_OBJ_COMMIT)
-		return git__throw(GIT_EOBJCORRUPTED, "HEAD is not a commit");
-
-	return 1;
+	return exists;
 }
 
 int git_repository_head(git_reference **head_out, git_repository *repo)
@@ -839,32 +791,35 @@ int git_repository_head(git_reference **head_out, git_repository *repo)
 	*head_out = NULL;
 
 	error = git_reference_lookup(&ref, repo, GIT_HEAD_FILE);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(GIT_ENOTAREPO, "Failed to locate the HEAD");
+	if (error < 0)
+		return error;
 
 	error = git_reference_resolve(&resolved_ref, ref);
-	if (error < GIT_SUCCESS) {
+	if (error < 0) {
 		git_reference_free(ref);
-		return git__rethrow(error, "Failed to resolve the HEAD");
+		return error;
 	}
 
 	git_reference_free(ref);
-
 	*head_out = resolved_ref;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_repository_head_orphan(git_repository *repo)
 {
-	git_reference *ref;
+	git_reference *ref = NULL;
 	int error;
 
 	error = git_repository_head(&ref, repo);
+	git_reference_free(ref);
 
-	if (error == GIT_SUCCESS)
-		git_reference_free(ref);
+	if (error == GIT_ENOTFOUND)
+		return 1;
 
-	return error == GIT_ENOTFOUND ? 1 : error;
+	if (error < 0)
+		return -1;
+
+	return 0;
 }
 
 int git_repository_is_empty(git_repository *repo)
@@ -872,9 +827,8 @@ int git_repository_is_empty(git_repository *repo)
 	git_reference *head = NULL, *branch = NULL;
 	int error;
 
-	error = git_reference_lookup(&head, repo, "HEAD");
-	if (error < GIT_SUCCESS)
-		return git__throw(error, "Corrupted repository. HEAD does not exist");
+	if (git_reference_lookup(&head, repo, "HEAD") < 0)
+		return -1;
 
 	if (git_reference_type(head) != GIT_REF_SYMBOLIC) {
 		git_reference_free(head);
@@ -891,7 +845,13 @@ int git_repository_is_empty(git_repository *repo)
 	git_reference_free(head);
 	git_reference_free(branch);
 
-	return error == GIT_ENOTFOUND ? 1 : error;
+	if (error == GIT_ENOTFOUND)
+		return 1;
+
+	if (error < 0)
+		return -1;
+
+	return 0;
 }
 
 const char *git_repository_path(git_repository *repo)
@@ -917,8 +877,7 @@ int git_repository_set_workdir(git_repository *repo, const char *workdir)
 	free(repo->workdir);
 
 	repo->workdir = git__strdup(workdir);
-	if (repo->workdir == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(repo->workdir);
 
 	repo->is_bare = 0;
 	return GIT_SUCCESS;
diff --git a/src/status.c b/src/status.c
index e80fc02..6315d63 100644
--- a/src/status.c
+++ b/src/status.c
@@ -423,10 +423,8 @@ static int dirent_cb(void *state, git_buf *a)
 			if (git_tree_entry_type(m) == GIT_OBJ_TREE)
 				git_path_to_dir(&st->head_tree_relative_path);
 
-			error = git_buf_lasterror(&st->head_tree_relative_path);
-			if (error < GIT_SUCCESS)
-				return git__rethrow(error, "An error occured while "
-					"determining the status of '%s'", a->ptr);
+			if (git_buf_oom(&st->head_tree_relative_path))
+				return GIT_ENOMEM;
 
 			m_name = st->head_tree_relative_path.ptr;
 		} else
diff --git a/src/tag.c b/src/tag.c
index 6076eb6..a5089e7 100644
--- a/src/tag.c
+++ b/src/tag.c
@@ -193,10 +193,9 @@ static int write_tag_annotation(
 	git_buf_putc(&tag, '\n');
 	git_buf_puts(&tag, message);
 
-	error = git_buf_lasterror(&tag);
-	if (error < GIT_SUCCESS) {
+	if (git_buf_oom(&tag)) {
 		git_buf_free(&tag);
-		return git__rethrow(error, "Not enough memory to build the tag data");
+		return git__throw(GIT_ENOMEM, "Not enough memory to build the tag data");
 	}
 
 	error = git_repository_odb__weakptr(&odb, repo);
diff --git a/src/transports/git.c b/src/transports/git.c
index 88e7e81..befdec5 100644
--- a/src/transports/git.c
+++ b/src/transports/git.c
@@ -68,7 +68,10 @@ static int gen_proto(git_buf *request, const char *cmd, const char *url)
 	git_buf_put(request, url, delim - url);
 	git_buf_putc(request, '\0');
 
-	return git_buf_lasterror(request);
+	if (git_buf_oom(request))
+		return GIT_ENOMEM;
+
+	return 0;
 }
 
 static int send_request(GIT_SOCKET s, const char *cmd, const char *url)
diff --git a/src/transports/http.c b/src/transports/http.c
index 2842d08..f16a802 100644
--- a/src/transports/http.c
+++ b/src/transports/http.c
@@ -77,7 +77,10 @@ static int gen_request(git_buf *buf, const char *url, const char *host, const ch
 	}
 	git_buf_puts(buf, "\r\n");
 
-	return git_buf_lasterror(buf);
+	if (git_buf_oom(buf))
+		return GIT_ENOMEM;
+
+	return 0;
 }
 
 static int do_connect(transport_http *t, const char *host, const char *port)
diff --git a/src/tree.c b/src/tree.c
index 19681e3..5957f7a 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -569,9 +569,9 @@ int git_treebuilder_write(git_oid *oid, git_repository *repo, git_treebuilder *b
 		git_buf_put(&tree, (char *)entry->oid.id, GIT_OID_RAWSZ);
 	}
 
-	if ((error = git_buf_lasterror(&tree)) < GIT_SUCCESS) {
+	if (git_buf_oom(&tree)) {
 		git_buf_free(&tree);
-		return git__rethrow(error, "Not enough memory to build the tree data");
+		return git__throw(GIT_ENOMEM, "Not enough memory to build the tree data");
 	}
 
 	error = git_repository_odb__weakptr(&odb, repo);
@@ -720,8 +720,9 @@ static int tree_walk_post(
 			/* append the next entry to the path */
 			git_buf_puts(path, entry->filename);
 			git_buf_putc(path, '/');
-			if ((error = git_buf_lasterror(path)) < GIT_SUCCESS)
-				break;
+
+			if (git_buf_oom(path))
+				return GIT_ENOMEM;
 
 			error = tree_walk_post(subtree, callback, path, payload);
 			if (error < GIT_SUCCESS)
diff --git a/src/util.h b/src/util.h
index f77c91d..803c63d 100644
--- a/src/util.h
+++ b/src/util.h
@@ -7,6 +7,8 @@
 #ifndef INCLUDE_util_h__
 #define INCLUDE_util_h__
 
+#include "git2/errors.h"
+
 #define ARRAY_SIZE(x) (sizeof(x)/sizeof(x[0]))
 #define bitsizeof(x) (CHAR_BIT * sizeof(x))
 #define MSB(x, bits) ((x) & (~0ULL << (bitsizeof(x) - (bits))))
@@ -23,7 +25,7 @@ GIT_INLINE(void *) git__malloc(size_t len)
 {
 	void *ptr = malloc(len);
 	if (!ptr)
-		git__throw(GIT_ENOMEM, "Out of memory. Failed to allocate %d bytes.", (int)len);
+		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to allocate %d bytes.", (int)len);
 	return ptr;
 }
 
@@ -31,7 +33,7 @@ GIT_INLINE(void *) git__calloc(size_t nelem, size_t elsize)
 {
 	void *ptr = calloc(nelem, elsize);
 	if (!ptr)
-		git__throw(GIT_ENOMEM, "Out of memory. Failed to allocate %d bytes.", (int)elsize);
+		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to allocate %d bytes.", (int)nelem*elsize);
 	return ptr;
 }
 
@@ -39,7 +41,7 @@ GIT_INLINE(char *) git__strdup(const char *str)
 {
 	char *ptr = strdup(str);
 	if (!ptr)
-		git__throw(GIT_ENOMEM, "Out of memory. Failed to duplicate string");
+		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to duplicate string");
 	return ptr;
 }
 
@@ -54,7 +56,7 @@ GIT_INLINE(char *) git__strndup(const char *str, size_t n)
 
 	ptr = (char*)malloc(length + 1);
 	if (!ptr) {
-		git__throw(GIT_ENOMEM, "Out of memory. Failed to duplicate string");
+		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to duplicate string");
 		return NULL;
 	}
 
@@ -68,7 +70,7 @@ GIT_INLINE(void *) git__realloc(void *ptr, size_t size)
 {
 	void *new_ptr = realloc(ptr, size);
 	if (!new_ptr)
-		git__throw(GIT_ENOMEM, "Out of memory. Failed to allocate %d bytes.", (int)size);
+		giterr_set(GITERR_NOMEMORY, "Out of memory. Failed to allocate %d bytes.", (int)size);
 	return new_ptr;
 }
 
diff --git a/src/win32/posix_w32.c b/src/win32/posix_w32.c
index 8e70719..2d7c2e3 100644
--- a/src/win32/posix_w32.c
+++ b/src/win32/posix_w32.c
@@ -1,4 +1,4 @@
-/*
+/ < 0)
  * Copyright (C) 2009-2012 the libgit2 contributors
  *
  * This file is part of libgit2, distributed under the GNU GPL v2 with
@@ -288,18 +288,13 @@ int p_rmdir(const char* path)
 
 int p_hide_directory__w32(const char *path)
 {
-	int error;
+	int res;
 	wchar_t* buf = gitwin_to_utf16(path);
 
-	error = SetFileAttributesW(buf, FILE_ATTRIBUTE_HIDDEN) != 0 ?
-		GIT_SUCCESS : GIT_ERROR; /* MSDN states a "non zero" value indicates a success */
-
+	res = SetFileAttributesW(buf, FILE_ATTRIBUTE_HIDDEN);
 	git__free(buf);
-
-	if (error < GIT_SUCCESS)
-		error = git__throw(GIT_EOSERR, "Failed to hide directory '%s'", path);
-
-	return error;
+	
+	return (res != 0) ?  GIT_SUCCESS : GIT_ERROR; /* MSDN states a "non zero" value indicates a success */
 }
 
 char *p_realpath(const char *orig_path, char *buffer)
diff --git a/tests/t12-repo.c b/tests/t12-repo.c
index 7c45e01..764af15 100644
--- a/tests/t12-repo.c
+++ b/tests/t12-repo.c
@@ -99,11 +99,15 @@ static int append_ceiling_dir(git_buf *ceiling_dirs, const char *path)
 
 	if (ceiling_dirs->size > 0)
 		git_buf_puts(ceiling_dirs, ceiling_separator);
+
 	git_buf_puts(ceiling_dirs, pretty_path.ptr);
 
 	git_buf_free(&pretty_path);
 
-	return git_buf_lasterror(ceiling_dirs);
+	if (git_buf_oom(ceiling_dirs))
+		return GIT_ENOMEM;
+
+	return 0;
 }
 
 BEGIN_TEST(discover0, "test discover")
@@ -119,7 +123,7 @@ BEGIN_TEST(discover0, "test discover")
 	must_pass(append_ceiling_dir(&ceiling_dirs_buf, TEMP_REPO_FOLDER));
 	ceiling_dirs = git_buf_cstr(&ceiling_dirs_buf);
 
-	must_be_true(git_repository_discover(repository_path, sizeof(repository_path), DISCOVER_FOLDER, 0, ceiling_dirs) == GIT_ENOTAREPO);
+	must_fail(git_repository_discover(repository_path, sizeof(repository_path), DISCOVER_FOLDER, 0, ceiling_dirs));
 
 	must_pass(git_repository_init(&repo, DISCOVER_FOLDER, 1));
 	must_pass(git_repository_discover(repository_path, sizeof(repository_path), DISCOVER_FOLDER, 0, ceiling_dirs));