thodg/libgit2

diff --git a/include/git2/errors.h b/include/git2/errors.h
index 5a4e540..d71df59 100644
--- a/include/git2/errors.h
+++ b/include/git2/errors.h
@@ -123,12 +123,14 @@ typedef struct {
 typedef enum {
 	GITERR_NOMEMORY,
 	GITERR_OS,
+	GITERR_INVALID,
 	GITERR_REFERENCE,
 	GITERR_ZLIB,
 	GITERR_REPOSITORY,
 	GITERR_CONFIG,
 	GITERR_REGEX,
-	GITERR_ODB
+	GITERR_ODB,
+	GITERR_INDEX
 } git_error_class;
 
 /**
diff --git a/src/fileops.c b/src/fileops.c
index 65942ad..f1f820a 100644
--- a/src/fileops.c
+++ b/src/fileops.c
@@ -108,10 +108,10 @@ mode_t git_futils_canonical_mode(mode_t raw_mode)
 		return S_IFREG | GIT_CANONICAL_PERMS(raw_mode);
 	else if (S_ISLNK(raw_mode))
 		return S_IFLNK;
-	else if (S_ISDIR(raw_mode))
-		return S_IFDIR;
 	else if (S_ISGITLINK(raw_mode))
 		return S_IFGITLINK;
+	else if (S_ISDIR(raw_mode))
+		return S_IFDIR;
 	else
 		return 0;
 }
diff --git a/src/index.c b/src/index.c
index 7f5909a..216ede7 100644
--- a/src/index.c
+++ b/src/index.c
@@ -135,19 +135,14 @@ int git_index_open(git_index **index_out, const char *index_path)
 
 	assert(index_out && index_path);
 
-	index = git__malloc(sizeof(git_index));
-	if (index == NULL)
-		return GIT_ENOMEM;
-
-	memset(index, 0x0, sizeof(git_index));
+	index = git__calloc(1, sizeof(git_index));
+	GITERR_CHECK_ALLOC(index);
 
 	index->index_file_path = git__strdup(index_path);
-	if (index->index_file_path == NULL) {
-		git__free(index);
-		return GIT_ENOMEM;
-	}
+	GITERR_CHECK_ALLOC(index->index_file_path);
 
-	git_vector_init(&index->entries, 32, index_cmp);
+	if (git_vector_init(&index->entries, 32, index_cmp) < 0)
+		return -1;
 
 	/* Check if index file is stored on disk already */
 	if (git_path_exists(index->index_file_path) == true)
@@ -215,7 +210,7 @@ void git_index_clear(git_index *index)
 
 int git_index_read(git_index *index)
 {
-	int error = GIT_SUCCESS, updated;
+	int error, updated;
 	git_buf buffer = GIT_BUF_INIT;
 	time_t mtime;
 
@@ -224,27 +219,26 @@ int git_index_read(git_index *index)
 	if (!index->on_disk || git_path_exists(index->index_file_path) == false) {
 		git_index_clear(index);
 		index->on_disk = 0;
-		return GIT_SUCCESS;
+		return 0;
 	}
 
 	/* We don't want to update the mtime if we fail to parse the index */
 	mtime = index->last_modified;
-	error = git_futils_readbuffer_updated(&buffer, index->index_file_path, &mtime, &updated);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to read index");
+	error = git_futils_readbuffer_updated(
+		&buffer, index->index_file_path, &mtime, &updated);
+	if (error < 0)
+		return error;
 
 	if (updated) {
 		git_index_clear(index);
 		error = parse_index(index, buffer.ptr, buffer.size);
 
-		if (error == GIT_SUCCESS)
+		if (!error)
 			index->last_modified = mtime;
 
 		git_buf_free(&buffer);
 	}
 
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to parse index");
 	return error;
 }
 
@@ -256,23 +250,24 @@ int git_index_write(git_index *index)
 
 	git_vector_sort(&index->entries);
 
-	if ((error = git_filebuf_open(&file, index->index_file_path, GIT_FILEBUF_HASH_CONTENTS)) < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to write index");
+	if ((error = git_filebuf_open(
+			 &file, index->index_file_path, GIT_FILEBUF_HASH_CONTENTS)) < 0)
+		return error;
 
-	if ((error = write_index(index, &file)) < GIT_SUCCESS) {
+	if ((error = write_index(index, &file)) < 0) {
 		git_filebuf_cleanup(&file);
-		return git__rethrow(error, "Failed to write index");
+		return error;
 	}
 
-	if ((error = git_filebuf_commit(&file, GIT_INDEX_FILE_MODE)) < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to write index");
+	if ((error = git_filebuf_commit(&file, GIT_INDEX_FILE_MODE)) < 0)
+		return error;
 
 	if (p_stat(index->index_file_path, &indexst) == 0) {
 		index->last_modified = indexst.st_mtime;
 		index->on_disk = 1;
 	}
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 unsigned int git_index_entrycount(git_index *index)
@@ -293,6 +288,20 @@ git_index_entry *git_index_get(git_index *index, unsigned int n)
 	return git_vector_get(&index->entries, n);
 }
 
+void git_index__init_entry_from_stat(struct stat *st, git_index_entry *entry)
+{
+	entry->ctime.seconds = (git_time_t)st->st_ctime;
+	entry->mtime.seconds = (git_time_t)st->st_mtime;
+	/* entry->mtime.nanoseconds = st->st_mtimensec; */
+	/* entry->ctime.nanoseconds = st->st_ctimensec; */
+	entry->dev  = st->st_rdev;
+	entry->ino  = st->st_ino;
+	entry->mode = index_create_mode(st->st_mode);
+	entry->uid  = st->st_uid;
+	entry->gid  = st->st_gid;
+	entry->file_size = st->st_size;
+}
+
 static int index_entry_init(git_index_entry **entry_out, git_index *index, const char *rel_path, int stage)
 {
 	git_index_entry *entry = NULL;
@@ -302,21 +311,17 @@ static int index_entry_init(git_index_entry **entry_out, git_index *index, const
 	git_buf full_path = GIT_BUF_INIT;
 	int error;
 
-	if (INDEX_OWNER(index) == NULL)
-		return git__throw(GIT_EBAREINDEX,
-			"Failed to initialize entry. Repository is bare");
-
-	if (stage < 0 || stage > 3)
-		return git__throw(GIT_ERROR,
-			"Failed to initialize entry. Invalid stage %i", stage);
+	assert(stage >= 0 && stage <= 3);
 
-	workdir = git_repository_workdir(INDEX_OWNER(index));
-	if (workdir == NULL)
-		return git__throw(GIT_EBAREINDEX,
-			"Failed to initialize entry. Cannot resolved workdir");
+	if (INDEX_OWNER(index) == NULL ||
+		(workdir = git_repository_workdir(INDEX_OWNER(index))) == NULL)
+	{
+		giterr_set(GITERR_INDEX,
+			"Could not initialize index entry. Repository is bare");
+		return -1;
+	}
 
-	error = git_buf_joinpath(&full_path, workdir, rel_path);
-	if (error < GIT_SUCCESS)
+	if ((error = git_buf_joinpath(&full_path, workdir, rel_path)) < 0)
 		return error;
 
 	if ((error = git_path_lstat(full_path.ptr, &st)) < 0) {
@@ -331,34 +336,21 @@ static int index_entry_init(git_index_entry **entry_out, git_index *index, const
 	 */
 
 	/* write the blob to disk and get the oid */
-	if ((error = git_blob_create_fromfile(&oid, INDEX_OWNER(index), rel_path)) < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to initialize index entry");
+	if ((error = git_blob_create_fromfile(&oid, INDEX_OWNER(index), rel_path)) < 0)
+		return error;
 
 	entry = git__calloc(1, sizeof(git_index_entry));
-	if (!entry)
-		return GIT_ENOMEM;
-
-	entry->ctime.seconds = (git_time_t)st.st_ctime;
-	entry->mtime.seconds = (git_time_t)st.st_mtime;
-	/* entry.mtime.nanoseconds = st.st_mtimensec; */
-	/* entry.ctime.nanoseconds = st.st_ctimensec; */
-	entry->dev= st.st_rdev;
-	entry->ino = st.st_ino;
-	entry->mode = index_create_mode(st.st_mode);
-	entry->uid = st.st_uid;
-	entry->gid = st.st_gid;
-	entry->file_size = st.st_size;
-	entry->oid = oid;
+	GITERR_CHECK_ALLOC(entry);
 
+	git_index__init_entry_from_stat(&st, entry);
+
+	entry->oid = oid;
 	entry->flags |= (stage << GIT_IDXENTRY_STAGESHIFT);
 	entry->path = git__strdup(rel_path);
-	if (entry->path == NULL) {
-		git__free(entry);
-		return GIT_ENOMEM;
-	}
+	GITERR_CHECK_ALLOC(entry->path);
 
 	*entry_out = entry;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static git_index_entry *index_entry_dup(const git_index_entry *source_entry)
@@ -393,10 +385,7 @@ static int index_insert(git_index *index, git_index_entry *entry, int replace)
 	int position;
 	git_index_entry **entry_array;
 
-	assert(index && entry);
-
-	if (entry->path == NULL)
-		return git__throw(GIT_EMISSINGOBJDATA, "Failed to insert into index. Entry has no path");
+	assert(index && entry && entry->path != NULL);
 
 	/* make sure that the path length flag is correct */
 	path_length = strlen(entry->path);
@@ -412,12 +401,8 @@ static int index_insert(git_index *index, git_index_entry *entry, int replace)
 	 * replacing is not requested: just insert entry at the end;
 	 * the index is no longer sorted
 	 */
-	if (!replace) {
-		if (git_vector_insert(&index->entries, entry) < GIT_SUCCESS)
-			return GIT_ENOMEM;
-
-		return GIT_SUCCESS;
-	}
+	if (!replace)
+		return git_vector_insert(&index->entries, entry);
 
 	/* look if an entry with this path already exists */
 	position = git_index_find(index, entry->path);
@@ -426,12 +411,8 @@ static int index_insert(git_index *index, git_index_entry *entry, int replace)
 	 * if no entry exists add the entry at the end;
 	 * the index is no longer sorted
 	 */
-	if (position == GIT_ENOTFOUND) {
-		if (git_vector_insert(&index->entries, entry) < GIT_SUCCESS)
-			return GIT_ENOMEM;
-
-		return GIT_SUCCESS;
-	}
+	if (position == GIT_ENOTFOUND)
+		return git_vector_insert(&index->entries, entry);
 
 	/* exists, replace it */
 	entry_array = (git_index_entry **) index->entries.contents;
@@ -439,7 +420,7 @@ static int index_insert(git_index *index, git_index_entry *entry, int replace)
 	git__free(entry_array[position]);
 	entry_array[position] = entry;
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int index_add(git_index *index, const char *path, int stage, int replace)
@@ -447,20 +428,15 @@ static int index_add(git_index *index, const char *path, int stage, int replace)
 	git_index_entry *entry = NULL;
 	int ret;
 
-	ret = index_entry_init(&entry, index, path, stage);
-	if (ret)
-		goto err;
-
-	ret = index_insert(index, entry, replace);
-	if (ret)
-		goto err;
+	if ((ret = index_entry_init(&entry, index, path, stage)) < 0 ||
+		(ret = index_insert(index, entry, replace)) < 0)
+	{
+		index_entry_free(entry);
+		return ret;
+	}
 
 	git_tree_cache_invalidate_path(index->tree, entry->path);
-
-	return ret;
-err:
-	index_entry_free(entry);
-	return git__rethrow(ret, "Failed to append to index");
+	return 0;
 }
 
 int git_index_add(git_index *index, const char *path, int stage)
@@ -473,28 +449,23 @@ int git_index_append(git_index *index, const char *path, int stage)
 	return index_add(index, path, stage, 0);
 }
 
-static int index_add2(git_index *index, const git_index_entry *source_entry,
-		int replace)
+static int index_add2(
+	git_index *index, const git_index_entry *source_entry, int replace)
 {
 	git_index_entry *entry = NULL;
 	int ret;
 
 	entry = index_entry_dup(source_entry);
-	if (entry == NULL) {
-		ret = GIT_ENOMEM;
-		goto err;
-	}
+	if (entry == NULL)
+		return -1;
 
-	ret = index_insert(index, entry, replace);
-	if (ret)
-		goto err;
+	if ((ret = index_insert(index, entry, replace)) < 0) {
+		index_entry_free(entry);
+		return ret;
+	}
 
 	git_tree_cache_invalidate_path(index->tree, entry->path);
-
-	return ret;
-err:
-	index_entry_free(entry);
-	return git__rethrow(ret, "Failed to append to index");
+	return 0;
 }
 
 int git_index_add2(git_index *index, const git_index_entry *source_entry)
@@ -513,13 +484,14 @@ int git_index_remove(git_index *index, int position)
 	git_index_entry *entry;
 
 	git_vector_sort(&index->entries);
+
 	entry = git_vector_get(&index->entries, position);
 	if (entry != NULL)
 		git_tree_cache_invalidate_path(index->tree, entry->path);
 
 	error = git_vector_remove(&index->entries, (unsigned int)position);
 
-	if (error == GIT_SUCCESS)
+	if (!error)
 		index_entry_free(entry);
 
 	return error;
@@ -535,7 +507,8 @@ void git_index_uniq(git_index *index)
 	git_vector_uniq(&index->entries);
 }
 
-const git_index_entry_unmerged *git_index_get_unmerged_bypath(git_index *index, const char *path)
+const git_index_entry_unmerged *git_index_get_unmerged_bypath(
+	git_index *index, const char *path)
 {
 	int pos;
 	assert(index && path);
@@ -549,69 +522,81 @@ const git_index_entry_unmerged *git_index_get_unmerged_bypath(git_index *index, 
 	return git_vector_get(&index->unmerged, pos);
 }
 
-const git_index_entry_unmerged *git_index_get_unmerged_byindex(git_index *index, unsigned int n)
+const git_index_entry_unmerged *git_index_get_unmerged_byindex(
+	git_index *index, unsigned int n)
 {
 	assert(index);
 	return git_vector_get(&index->unmerged, n);
 }
 
+static int index_error_invalid(const char *message)
+{
+	giterr_set(GITERR_INDEX, "Invalid data in index - %s", message);
+	return -1;
+}
+
 static int read_unmerged(git_index *index, const char *buffer, size_t size)
 {
 	const char *endptr;
 	size_t len;
 	int i;
 
-	git_vector_init(&index->unmerged, 16, unmerged_cmp);
+	if (git_vector_init(&index->unmerged, 16, unmerged_cmp) < 0)
+		return -1;
 
 	while (size) {
 		git_index_entry_unmerged *lost;
 
 		len = strlen(buffer) + 1;
 		if (size <= len)
-			return git__throw(GIT_ERROR, "Failed to read unmerged entries");
+			return index_error_invalid("reading unmerged entries");
 
-		if ((lost = git__malloc(sizeof(git_index_entry_unmerged))) == NULL)
-			return GIT_ENOMEM;
+		lost = git__malloc(sizeof(git_index_entry_unmerged));
+		GITERR_CHECK_ALLOC(lost);
 
-		if (git_vector_insert(&index->unmerged, lost) < GIT_SUCCESS)
-			return git__throw(GIT_ERROR, "Failed to read unmerged entries");
+		if (git_vector_insert(&index->unmerged, lost) < 0)
+			return -1;
 
+		/* read NUL-terminated pathname for entry */
 		lost->path = git__strdup(buffer);
-		if (!lost->path)
-			return GIT_ENOMEM;
+		GITERR_CHECK_ALLOC(lost->path);
 
 		size -= len;
 		buffer += len;
 
+		/* read 3 ASCII octal numbers for stage entries */
 		for (i = 0; i < 3; i++) {
 			int tmp;
 
-			if (git__strtol32(&tmp, buffer, &endptr, 8) < GIT_SUCCESS ||
-				!endptr || endptr == buffer || *endptr || (unsigned)tmp > UINT_MAX)
-				return GIT_ERROR;
+			if (git__strtol32(&tmp, buffer, &endptr, 8) < 0 ||
+				!endptr || endptr == buffer || *endptr ||
+				(unsigned)tmp > UINT_MAX)
+				return index_error_invalid("reading unmerged entry stage");
 
 			lost->mode[i] = tmp;
 
 			len = (endptr + 1) - buffer;
 			if (size <= len)
-				return git__throw(GIT_ERROR, "Failed to read unmerged entries");
+				return index_error_invalid("reading unmerged entry stage");
 
 			size -= len;
 			buffer += len;
 		}
 
+		/* read up to 3 OIDs for stage entries */
 		for (i = 0; i < 3; i++) {
 			if (!lost->mode[i])
 				continue;
 			if (size < 20)
-				return git__throw(GIT_ERROR, "Failed to read unmerged entries");
+				return index_error_invalid("reading unmerged entry oid");
+
 			git_oid_fromraw(&lost->oid[i], (const unsigned char *) buffer);
 			size -= 20;
 			buffer += 20;
 		}
 	}
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static size_t read_entry(git_index_entry *dest, const void *buffer, size_t buffer_size)
@@ -657,7 +642,7 @@ static size_t read_entry(git_index_entry *dest, const void *buffer, size_t buffe
 
 		path_end = memchr(path_ptr, '\0', buffer_size);
 		if (path_end == NULL)
-				return 0;
+			return 0;
 
 		path_length = path_end - path_ptr;
 	}
@@ -682,15 +667,15 @@ static int read_header(struct index_header *dest, const void *buffer)
 
 	dest->signature = ntohl(source->signature);
 	if (dest->signature != INDEX_HEADER_SIG)
-		return GIT_EOBJCORRUPTED;
+		return index_error_invalid("incorrect header signature");
 
 	dest->version = ntohl(source->version);
 	if (dest->version != INDEX_VERSION_NUMBER_EXT &&
 		dest->version != INDEX_VERSION_NUMBER)
-		return GIT_EOBJCORRUPTED;
+		return index_error_invalid("incorrect header version");
 
 	dest->entry_count = ntohl(source->entry_count);
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static size_t read_extension(git_index *index, const char *buffer, size_t buffer_size)
@@ -713,10 +698,10 @@ static size_t read_extension(git_index *index, const char *buffer, size_t buffer
 	if (dest.signature[0] >= 'A' && dest.signature[0] <= 'Z') {
 		/* tree cache */
 		if (memcmp(dest.signature, INDEX_EXT_TREECACHE_SIG, 4) == 0) {
-			if (git_tree_cache_read(&index->tree, buffer + 8, dest.extension_size) < GIT_SUCCESS)
+			if (git_tree_cache_read(&index->tree, buffer + 8, dest.extension_size) < 0)
 				return 0;
 		} else if (memcmp(dest.signature, INDEX_EXT_UNMERGED_SIG, 4) == 0) {
-			if (read_unmerged(index, buffer + 8, dest.extension_size) < GIT_SUCCESS)
+			if (read_unmerged(index, buffer + 8, dest.extension_size) < 0)
 				return 0;
 		}
 		/* else, unsupported extension. We cannot parse this, but we can skip
@@ -738,21 +723,21 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 
 #define seek_forward(_increase) { \
 	if (_increase >= buffer_size) \
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to seek forward. Buffer size exceeded"); \
+		return index_error_invalid("ran out of data while parsing"); \
 	buffer += _increase; \
 	buffer_size -= _increase;\
 }
 
 	if (buffer_size < INDEX_HEADER_SIZE + INDEX_FOOTER_SIZE)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse index. Buffer too small");
+		return index_error_invalid("insufficient buffer space");
 
 	/* Precalculate the SHA1 of the files's contents -- we'll match it to
 	 * the provided SHA1 in the footer */
 	git_hash_buf(&checksum_calculated, buffer, buffer_size - INDEX_FOOTER_SIZE);
 
 	/* Parse header */
-	if (read_header(&header, buffer) < GIT_SUCCESS)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse index. Header is corrupted");
+	if (read_header(&header, buffer) < 0)
+		return -1;
 
 	seek_forward(INDEX_HEADER_SIZE);
 
@@ -764,23 +749,22 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 		git_index_entry *entry;
 
 		entry = git__malloc(sizeof(git_index_entry));
-		if (entry == NULL)
-			return GIT_ENOMEM;
+		GITERR_CHECK_ALLOC(entry);
 
 		entry_size = read_entry(entry, buffer, buffer_size);
 
 		/* 0 bytes read means an object corruption */
 		if (entry_size == 0)
-			return git__throw(GIT_EOBJCORRUPTED, "Failed to parse index. Entry size is zero");
+			return index_error_invalid("invalid entry");
 
-		if (git_vector_insert(&index->entries, entry) < GIT_SUCCESS)
-			return GIT_ENOMEM;
+		if (git_vector_insert(&index->entries, entry) < 0)
+			return -1;
 
 		seek_forward(entry_size);
 	}
 
 	if (i != header.entry_count)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse index. Header entries changed while parsing");
+		return index_error_invalid("header entries changed while parsing");
 
 	/* There's still space for some extensions! */
 	while (buffer_size > INDEX_FOOTER_SIZE) {
@@ -790,43 +774,43 @@ static int parse_index(git_index *index, const char *buffer, size_t buffer_size)
 
 		/* see if we have read any bytes from the extension */
 		if (extension_size == 0)
-			return git__throw(GIT_EOBJCORRUPTED, "Failed to parse index. Extension size is zero");
+			return index_error_invalid("extension size is zero");
 
 		seek_forward(extension_size);
 	}
 
 	if (buffer_size != INDEX_FOOTER_SIZE)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse index. Buffer size does not match index footer size");
+		return index_error_invalid("buffer size does not match index footer size");
 
 	/* 160-bit SHA-1 over the content of the index file before this checksum. */
 	git_oid_fromraw(&checksum_expected, (const unsigned char *)buffer);
 
 	if (git_oid_cmp(&checksum_calculated, &checksum_expected) != 0)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse index. Calculated checksum does not match expected checksum");
+		return index_error_invalid("calculated checksum does not match expected");
 
 #undef seek_forward
 
 	/* force sorting in the vector: the entries are
 	 * assured to be sorted on the index */
 	index->entries.sorted = 1;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int is_index_extended(git_index *index)
 {
 	unsigned int i, extended;
+	git_index_entry *entry;
 
 	extended = 0;
 
-	for (i = 0; i < index->entries.length; ++i) {
-		git_index_entry *entry;
-		entry = git_vector_get(&index->entries, i);
+	git_vector_foreach(&index->entries, i, entry) {
 		entry->flags &= ~GIT_IDXENTRY_EXTENDED;
 		if (entry->flags_extended & GIT_IDXENTRY_EXTENDED_FLAGS) {
 			extended++;
 			entry->flags |= GIT_IDXENTRY_EXTENDED;
 		}
 	}
+
 	return extended;
 }
 
@@ -844,8 +828,8 @@ static int write_disk_entry(git_filebuf *file, git_index_entry *entry)
 	else
 		disk_size = short_entry_size(path_len);
 
-	if (git_filebuf_reserve(file, &mem, disk_size) < GIT_SUCCESS)
-		return GIT_ENOMEM;
+	if (git_filebuf_reserve(file, &mem, disk_size) < 0)
+		return -1;
 
 	ondisk = (struct entry_short *)mem;
 
@@ -887,7 +871,7 @@ static int write_disk_entry(git_filebuf *file, git_index_entry *entry)
 
 	memcpy(path, entry->path, path_len);
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int write_entries(git_index *index, git_filebuf *file)
@@ -897,16 +881,15 @@ static int write_entries(git_index *index, git_filebuf *file)
 	for (i = 0; i < index->entries.length; ++i) {
 		git_index_entry *entry;
 		entry = git_vector_get(&index->entries, i);
-		if (write_disk_entry(file, entry) < GIT_SUCCESS)
-			return GIT_ENOMEM;
+		if (write_disk_entry(file, entry) < 0)
+			return -1;
 	}
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int write_index(git_index *index, git_filebuf *file)
 {
-	int error = GIT_SUCCESS;
 	git_oid hash_final;
 
 	struct index_header header;
@@ -921,11 +904,11 @@ static int write_index(git_index *index, git_filebuf *file)
 	header.version = htonl(is_extended ? INDEX_VERSION_NUMBER_EXT : INDEX_VERSION_NUMBER);
 	header.entry_count = htonl(index->entries.length);
 
-	git_filebuf_write(file, &header, sizeof(struct index_header));
+	if (git_filebuf_write(file, &header, sizeof(struct index_header)) < 0)
+		return -1;
 
-	error = write_entries(index, file);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to write index");
+	if (write_entries(index, file) < 0)
+		return -1;
 
 	/* TODO: write extensions (tree cache) */
 
@@ -933,9 +916,7 @@ static int write_index(git_index *index, git_filebuf *file)
 	git_filebuf_hash(&hash_final, file);
 
 	/* write it at the end of the file */
-	git_filebuf_write(file, hash_final.id, GIT_OID_RAWSZ);
-
-	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to write index");
+	return git_filebuf_write(file, hash_final.id, GIT_OID_RAWSZ);
 }
 
 int git_index_entry_stage(const git_index_entry *entry)
@@ -945,36 +926,30 @@ int git_index_entry_stage(const git_index_entry *entry)
 
 static int read_tree_cb(const char *root, git_tree_entry *tentry, void *data)
 {
-	int ret = GIT_SUCCESS;
 	git_index *index = data;
 	git_index_entry *entry = NULL;
 	git_buf path = GIT_BUF_INIT;
 
 	if (entry_is_tree(tentry))
-		goto exit;
+		return 0;
 
-	ret = git_buf_joinpath(&path, root, tentry->filename);
-	if (ret < GIT_SUCCESS)
-		goto exit;
+	if (git_buf_joinpath(&path, root, tentry->filename) < 0)
+		return -1;
 
 	entry = git__calloc(1, sizeof(git_index_entry));
-	if (!entry) {
-		ret = GIT_ENOMEM;
-		goto exit;
-	}
+	GITERR_CHECK_ALLOC(entry);
 
 	entry->mode = tentry->attr;
 	entry->oid = tentry->oid;
 	entry->path = git_buf_detach(&path);
-
-	ret = index_insert(index, entry, 0);
-
-exit:
 	git_buf_free(&path);
 
-	if (ret < GIT_SUCCESS)
+	if (index_insert(index, entry, 0) < 0) {
 		index_entry_free(entry);
-	return ret;
+		return -1;
+	}
+
+	return 0;
 }
 
 int git_index_read_tree(git_index *index, git_tree *tree)
diff --git a/src/index.h b/src/index.h
index 4f03652..e745c8f 100644
--- a/src/index.h
+++ b/src/index.h
@@ -31,4 +31,6 @@ struct git_index {
 	git_vector unmerged;
 };
 
+extern void git_index__init_entry_from_stat(struct stat *st, git_index_entry *entry);
+
 #endif
diff --git a/src/iterator.c b/src/iterator.c
index 5cc01cc..cc15b5f 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -395,7 +395,6 @@ static void workdir_iterator__free(git_iterator *self)
 
 static int workdir_iterator__update_entry(workdir_iterator *wi)
 {
-	int error;
 	git_path_with_stat *ps = git_vector_get(&wi->stack->entries, wi->stack->index);
 
 	git_buf_truncate(&wi->path, wi->root_len);
@@ -412,24 +411,18 @@ static int workdir_iterator__update_entry(workdir_iterator *wi)
 	/* if there is an error processing the entry, treat as ignored */
 	wi->is_ignored = 1;
 
-	/* TODO: remove shared code for struct stat conversion with index.c */
-	wi->entry.ctime.seconds = (git_time_t)ps->st.st_ctime;
-	wi->entry.mtime.seconds = (git_time_t)ps->st.st_mtime;
-	wi->entry.dev  = ps->st.st_rdev;
-	wi->entry.ino  = ps->st.st_ino;
+	git_index__init_entry_from_stat(&ps->st, &wi->entry);
+
+	/* need different mode here to keep directories during iteration */
 	wi->entry.mode = git_futils_canonical_mode(ps->st.st_mode);
-	wi->entry.uid  = ps->st.st_uid;
-	wi->entry.gid  = ps->st.st_gid;
-	wi->entry.file_size = ps->st.st_size;
 
 	/* if this is a file type we don't handle, treat as ignored */
 	if (wi->entry.mode == 0)
 		return 0;
 
 	/* okay, we are far enough along to look up real ignore rule */
-	error = git_ignore__lookup(&wi->ignores, wi->entry.path, &wi->is_ignored);
-	if (error < 0)
-		return 0;
+	if (git_ignore__lookup(&wi->ignores, wi->entry.path, &wi->is_ignored) < 0)
+		return 0; /* if error, ignore it and ignore file */
 
 	/* detect submodules */
 	if (S_ISDIR(wi->entry.mode) &&
diff --git a/src/oid.c b/src/oid.c
index a1f0109..4adccfb 100644
--- a/src/oid.c
+++ b/src/oid.c
@@ -13,13 +13,19 @@
 
 static char to_hex[] = "0123456789abcdef";
 
+static int oid_error_invalid(const char *msg)
+{
+	giterr_set(GITERR_INVALID, "Unable to parse OID - %s", msg);
+	return -1;
+}
+
 int git_oid_fromstrn(git_oid *out, const char *str, size_t length)
 {
 	size_t p;
 	int v;
 
 	if (length < 4)
-		return git__throw(GIT_ENOTOID, "Failed to generate sha1. Given string is too short");
+		return oid_error_invalid("input too short");
 
 	if (length > GIT_OID_HEXSZ)
 		length = GIT_OID_HEXSZ;
@@ -29,7 +35,7 @@ int git_oid_fromstrn(git_oid *out, const char *str, size_t length)
 				| git__fromhex(str[p + 1]);
 
 		if (v < 0)
-			return git__throw(GIT_ENOTOID, "Failed to generate sha1. Given string is not a valid sha1 hash");
+			return oid_error_invalid("contains invalid characters");
 
 		out->id[p / 2] = (unsigned char)v;
 	}
@@ -37,7 +43,7 @@ int git_oid_fromstrn(git_oid *out, const char *str, size_t length)
 	if (length % 2) {
 		v = (git__fromhex(str[p + 0]) << 4);
 		if (v < 0)
-			return git__throw(GIT_ENOTOID, "Failed to generate sha1. Given string is not a valid sha1 hash");
+			return oid_error_invalid("contains invalid characters");
 
 		out->id[p / 2] = (unsigned char)v;
 		p += 2;
@@ -45,7 +51,7 @@ int git_oid_fromstrn(git_oid *out, const char *str, size_t length)
 
 	memset(out->id + p / 2, 0, (GIT_OID_HEXSZ - p) / 2);
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_oid_fromstr(git_oid *out, const char *str)
@@ -109,8 +115,9 @@ char *git_oid_to_string(char *out, size_t n, const git_oid *oid)
 	return out;
 }
 
-int git_oid__parse(git_oid *oid, const char **buffer_out,
-		const char *buffer_end, const char *header)
+int git_oid__parse(
+	git_oid *oid, const char **buffer_out,
+	const char *buffer_end, const char *header)
 {
 	const size_t sha_len = GIT_OID_HEXSZ;
 	const size_t header_len = strlen(header);
@@ -118,20 +125,20 @@ int git_oid__parse(git_oid *oid, const char **buffer_out,
 	const char *buffer = *buffer_out;
 
 	if (buffer + (header_len + sha_len + 1) > buffer_end)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse OID. Buffer too small");
+		return oid_error_invalid("input is too short");
 
 	if (memcmp(buffer, header, header_len) != 0)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse OID. Buffer and header do not match");
+		return oid_error_invalid("did not match expected header");
 
 	if (buffer[header_len + sha_len] != '\n')
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse OID. Buffer not terminated correctly");
+		return oid_error_invalid("not terminated correctly");
 
-	if (git_oid_fromstr(oid, buffer + header_len) < GIT_SUCCESS)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse OID. Failed to generate sha1");
+	if (git_oid_fromstr(oid, buffer + header_len) < 0)
+		return -1;
 
 	*buffer_out = buffer + (header_len + sha_len + 1);
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 void git_oid__writebuf(git_buf *buf, const char *header, const git_oid *oid)
@@ -182,12 +189,11 @@ int git_oid_ncmp(const git_oid *oid_a, const git_oid *oid_b, unsigned int len)
 int git_oid_streq(const git_oid *a, const char *str)
 {
 	git_oid id;
-	int error;
 
-	if ((error = git_oid_fromstr(&id, str)) < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to convert '%s' to oid.", str);
+	if (git_oid_fromstr(&id, str) < 0)
+		return -1;
 
-	return git_oid_cmp(a, &id) == 0 ? GIT_SUCCESS : GIT_ERROR;
+	return git_oid_cmp(a, &id) == 0 ? 0 : -1;
 }
 
 int git_oid_iszero(const git_oid *oid_a)
@@ -216,15 +222,14 @@ struct git_oid_shorten {
 static int resize_trie(git_oid_shorten *self, size_t new_size)
 {
 	self->nodes = git__realloc(self->nodes, new_size * sizeof(trie_node));
-	if (self->nodes == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(self->nodes);
 
 	if (new_size > self->size) {
 		memset(&self->nodes[self->size], 0x0, (new_size - self->size) * sizeof(trie_node));
 	}
 
 	self->size = new_size;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static trie_node *push_leaf(git_oid_shorten *os, node_index idx, int push_at, const char *oid)
@@ -233,7 +238,7 @@ static trie_node *push_leaf(git_oid_shorten *os, node_index idx, int push_at, co
 	node_index idx_leaf;
 
 	if (os->node_count >= os->size) {
-		if (resize_trie(os, os->size * 2) < GIT_SUCCESS)
+		if (resize_trie(os, os->size * 2) < 0)
 			return NULL;
 	}
 
@@ -255,13 +260,11 @@ git_oid_shorten *git_oid_shorten_new(size_t min_length)
 {
 	git_oid_shorten *os;
 
-	os = git__malloc(sizeof(git_oid_shorten));
+	os = git__calloc(1, sizeof(git_oid_shorten));
 	if (os == NULL)
 		return NULL;
 
-	memset(os, 0x0, sizeof(git_oid_shorten));
-
-	if (resize_trie(os, 16) < GIT_SUCCESS) {
+	if (resize_trie(os, 16) < 0) {
 		git__free(os);
 		return NULL;
 	}
@@ -329,7 +332,7 @@ int git_oid_shorten_add(git_oid_shorten *os, const char *text_oid)
 	node_index idx;
 
 	if (os->full)
-		return GIT_ENOMEM;
+		return -1;
 
 	if (text_oid == NULL)
 		return os->min_length;
@@ -341,8 +344,10 @@ int git_oid_shorten_add(git_oid_shorten *os, const char *text_oid)
 		int c = git__fromhex(text_oid[i]);
 		trie_node *node;
 
-		if (c == -1)
-			return git__throw(GIT_ENOTOID, "Failed to shorten OID. Invalid hex value");
+		if (c == -1) {
+			giterr_set(GITERR_INVALID, "Unable to shorten OID - invalid hex value");
+			return -1;
+		}
 
 		node = &os->nodes[idx];
 
@@ -353,13 +358,12 @@ int git_oid_shorten_add(git_oid_shorten *os, const char *text_oid)
 			node->tail = NULL;
 
 			node = push_leaf(os, idx, git__fromhex(tail[0]), &tail[1]);
-			if (node == NULL)
-				return GIT_ENOMEM;
+			GITERR_CHECK_ALLOC(node);
 		}
 
 		if (node->children[c] == 0) {
 			if (push_leaf(os, idx, c, &text_oid[i + 1]) == NULL)
-				return GIT_ENOMEM;
+				return -1;
 			break;
 		}
 
diff --git a/src/util.c b/src/util.c
index 679917e..d0ad474 100644
--- a/src/util.c
+++ b/src/util.c
@@ -112,34 +112,40 @@ int git__strtol64(int64_t *result, const char *nptr, const char **endptr, int ba
 	}
 
 Return:
-	if (ndig == 0)
-		return git__throw(GIT_ENOTNUM, "Failed to convert string to long. Not a number");
+	if (ndig == 0) {
+		giterr_set(GITERR_INVALID, "Failed to convert string to long. Not a number");
+		return -1;
+	}
 
 	if (endptr)
 		*endptr = p;
 
-	if (ovfl)
-		return git__throw(GIT_EOVERFLOW, "Failed to convert string to long. Overflow error");
+	if (ovfl) {
+		giterr_set(GITERR_INVALID, "Failed to convert string to long. Overflow error");
+		return -1;
+	}
 
 	*result = neg ? -n : n;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git__strtol32(int32_t *result, const char *nptr, const char **endptr, int base)
 {
-	int error = GIT_SUCCESS;
+	int error;
 	int32_t tmp_int;
 	int64_t tmp_long;
 
-	if ((error = git__strtol64(&tmp_long, nptr, endptr, base)) < GIT_SUCCESS)
+	if ((error = git__strtol64(&tmp_long, nptr, endptr, base)) < 0)
 		return error;
 
 	tmp_int = tmp_long & 0xFFFFFFFF;
-	if (tmp_int != tmp_long)
-		return git__throw(GIT_EOVERFLOW, "Failed to convert. '%s' is too large", nptr);
+	if (tmp_int != tmp_long) {
+		giterr_set(GITERR_INVALID, "Failed to convert. '%s' is too large", nptr);
+		return -1;
+	}
 
 	*result = tmp_int;
-	
+
 	return error;
 }
 
diff --git a/tests-clar/core/oid.c b/tests-clar/core/oid.c
index 60361c4..c897139 100644
--- a/tests-clar/core/oid.c
+++ b/tests-clar/core/oid.c
@@ -10,9 +10,9 @@ void test_core_oid__initialize(void)
 
 void test_core_oid__streq(void)
 {
-	cl_assert(git_oid_streq(&id, str_oid) == GIT_SUCCESS);
-	cl_assert(git_oid_streq(&id, "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef") == GIT_ERROR);
+	cl_assert(git_oid_streq(&id, str_oid) == 0);
+	cl_assert(git_oid_streq(&id, "deadbeefdeadbeefdeadbeefdeadbeefdeadbeef") == -1);
 
-	cl_assert(git_oid_streq(&id, "deadbeef") == GIT_ENOTOID);
-	cl_assert(git_oid_streq(&id, "I'm not an oid.... :)") == GIT_ENOTOID);
+	cl_assert(git_oid_streq(&id, "deadbeef") == -1);
+	cl_assert(git_oid_streq(&id, "I'm not an oid.... :)") == -1);
 }