thodg/libgit2

diff --git a/src/indexer.c b/src/indexer.c
index 6f8bd32..b5d6397 100644
--- a/src/indexer.c
+++ b/src/indexer.c
@@ -49,17 +49,22 @@ static int parse_header(git_indexer *idx)
 	int error;
 
 	/* Verify we recognize this pack file format. */
-	if ((error = p_read(idx->pack->mwf.fd, &idx->hdr, sizeof(idx->hdr))) < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to read in pack header");
-
-	if (idx->hdr.hdr_signature != ntohl(PACK_SIGNATURE))
-		return git__throw(GIT_EOBJCORRUPTED, "Wrong pack signature");
+	if ((error = p_read(idx->pack->mwf.fd, &idx->hdr, sizeof(idx->hdr))) < 0) {
+		giterr_set(GITERR_OS, "Failed to read in pack header");
+		return error;
+	}
 
-	if (!pack_version_ok(idx->hdr.hdr_version))
-		return git__throw(GIT_EOBJCORRUPTED, "Wrong pack version");
+	if (idx->hdr.hdr_signature != ntohl(PACK_SIGNATURE)) {
+		giterr_set(GITERR_INVALID, "Wrong pack signature");
+		return -1;
+	}
 
+	if (!pack_version_ok(idx->hdr.hdr_version)) {
+		giterr_set(GITERR_INVALID, "Wrong pack version");
+		return -1;
+	}
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int objects_cmp(const void *a, const void *b)
@@ -87,49 +92,43 @@ int git_indexer_new(git_indexer **out, const char *packname)
 
 	assert(out && packname);
 
-	if (git_path_root(packname) < 0)
-		return git__throw(GIT_EINVALIDPATH, "Path is not absolute");
-
-	idx = git__malloc(sizeof(git_indexer));
-	if (idx == NULL)
-		return GIT_ENOMEM;
+	if (git_path_root(packname) < 0) {
+		giterr_set(GITERR_INVALID, "Path is not absolute");
+		return -1;
+	}
 
-	memset(idx, 0x0, sizeof(*idx));
+	idx = git__calloc(1, sizeof(git_indexer));
+	GITERR_CHECK_ALLOC(idx);
 
 	namelen = strlen(packname);
-	idx->pack = git__malloc(sizeof(struct git_pack_file) + namelen + 1);
-	if (idx->pack == NULL) {
-		error = GIT_ENOMEM;
-		goto cleanup;
-	}
+	idx->pack = git__calloc(1, sizeof(struct git_pack_file) + namelen + 1);
+	GITERR_CHECK_ALLOC(idx->pack);
 
-	memset(idx->pack, 0x0, sizeof(struct git_pack_file));
 	memcpy(idx->pack->pack_name, packname, namelen + 1);
 
-	ret = p_stat(packname, &idx->st);
-	if (ret < 0) {
-		if (errno == ENOENT)
-			error = git__throw(GIT_ENOTFOUND, "Failed to stat packfile. File not found");
-		else
-			error = git__throw(GIT_EOSERR, "Failed to stat packfile.");
+	if ((ret = p_stat(packname, &idx->st)) < 0) {
+		if (errno == ENOENT) {
+			giterr_set(GITERR_OS, "Failed to stat packfile. File not found");
+			error = GIT_ENOTFOUND;
+		} else {
+			giterr_set(GITERR_OS, "Failed to stat packfile.");
+			error = -1;
+		}
 
 		goto cleanup;
 	}
 
-	ret = p_open(idx->pack->pack_name, O_RDONLY);
-	if (ret < 0) {
-		error = git__throw(GIT_EOSERR, "Failed to open packfile");
+	if ((ret = p_open(idx->pack->pack_name, O_RDONLY)) < 0) {
+		giterr_set(GITERR_OS, "Failed to open packfile.");
+		error = -1;
 		goto cleanup;
 	}
 
 	idx->pack->mwf.fd = ret;
 	idx->pack->mwf.size = (git_off_t)idx->st.st_size;
 
-	error = parse_header(idx);
-	if (error < GIT_SUCCESS) {
-		error = git__rethrow(error, "Failed to parse packfile header");
+	if ((error = parse_header(idx)) < 0)
 		goto cleanup;
-	}
 
 	idx->nr_objects = ntohl(idx->hdr.hdr_entries);
 
@@ -137,17 +136,17 @@ int git_indexer_new(git_indexer **out, const char *packname)
 	assert(idx->nr_objects == (size_t)((unsigned int)idx->nr_objects));
 
 	error = git_vector_init(&idx->pack->cache, (unsigned int)idx->nr_objects, cache_cmp);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		goto cleanup;
 
 	idx->pack->has_cache = 1;
 	error = git_vector_init(&idx->objects, (unsigned int)idx->nr_objects, objects_cmp);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		goto cleanup;
 
 	*out = idx;
 
-	return GIT_SUCCESS;
+	return 0;
 
 cleanup:
 	git_indexer_free(idx);
@@ -165,8 +164,8 @@ static int index_path(git_buf *path, git_indexer *idx)
 		slash--;
 
 	if (git_buf_grow(path, slash + 1 + strlen(prefix) +
-					 GIT_OID_HEXSZ + strlen(suffix) + 1) < GIT_SUCCESS)
-		return GIT_ENOMEM;
+					 GIT_OID_HEXSZ + strlen(suffix) + 1) < 0)
+		return -1;
 
 	git_buf_truncate(path, slash);
 	git_buf_puts(path, prefix);
@@ -174,10 +173,7 @@ static int index_path(git_buf *path, git_indexer *idx)
 	path->size += GIT_OID_HEXSZ;
 	git_buf_puts(path, suffix);
 
-	if (git_buf_oom(path))
-		return GIT_ENOMEM;
-
-	return 0;
+	return git_buf_oom(path) ? -1 : 0;
 }
 
 int git_indexer_write(git_indexer *idx)
@@ -197,26 +193,25 @@ int git_indexer_write(git_indexer *idx)
 	git_buf_sets(&filename, idx->pack->pack_name);
 	git_buf_truncate(&filename, filename.size - strlen("pack"));
 	git_buf_puts(&filename, "idx");
-
 	if (git_buf_oom(&filename))
-		return GIT_ENOMEM;
+		return -1;
 
 	error = git_filebuf_open(&idx->file, filename.ptr, GIT_FILEBUF_HASH_CONTENTS);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		goto cleanup;
 
 	/* Write out the header */
 	hdr.idx_signature = htonl(PACK_IDX_SIGNATURE);
 	hdr.idx_version = htonl(2);
 	error = git_filebuf_write(&idx->file, &hdr, sizeof(hdr));
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		goto cleanup;
 
 	/* Write out the fanout table */
 	for (i = 0; i < 256; ++i) {
 		uint32_t n = htonl(idx->fanout[i]);
 		error = git_filebuf_write(&idx->file, &n, sizeof(n));
-		if (error < GIT_SUCCESS)
+		if (error < 0)
 			goto cleanup;
 	}
 
@@ -225,7 +220,7 @@ int git_indexer_write(git_indexer *idx)
 	git_vector_foreach(&idx->objects, i, entry) {
 		error = git_filebuf_write(&idx->file, &entry->oid, sizeof(git_oid));
 		SHA1_Update(&ctx, &entry->oid, GIT_OID_RAWSZ);
-		if (error < GIT_SUCCESS)
+		if (error < 0)
 			goto cleanup;
 	}
 	SHA1_Final(idx->hash.id, &ctx);
@@ -233,7 +228,7 @@ int git_indexer_write(git_indexer *idx)
 	/* Write out the CRC32 values */
 	git_vector_foreach(&idx->objects, i, entry) {
 		error = git_filebuf_write(&idx->file, &entry->crc, sizeof(uint32_t));
-		if (error < GIT_SUCCESS)
+		if (error < 0)
 			goto cleanup;
 	}
 
@@ -247,7 +242,7 @@ int git_indexer_write(git_indexer *idx)
 			n = htonl(entry->offset);
 
 		error = git_filebuf_write(&idx->file, &n, sizeof(uint32_t));
-		if (error < GIT_SUCCESS)
+		if (error < 0)
 			goto cleanup;
 	}
 
@@ -262,7 +257,7 @@ int git_indexer_write(git_indexer *idx)
 		split[1] = htonl(entry->offset_long & 0xffffffff);
 
 		error = git_filebuf_write(&idx->file, &split, sizeof(uint32_t) * 2);
-		if (error < GIT_SUCCESS)
+		if (error < 0)
 			goto cleanup;
 	}
 
@@ -271,7 +266,7 @@ int git_indexer_write(git_indexer *idx)
 	packfile_hash = git_mwindow_open(&idx->pack->mwf, &w, idx->st.st_size - GIT_OID_RAWSZ, GIT_OID_RAWSZ, &left);
 	git_mwindow_close(&w);
 	if (packfile_hash == NULL) {
-		error = git__rethrow(GIT_ENOMEM, "Failed to open window to packfile hash");
+		error = -1;
 		goto cleanup;
 	}
 
@@ -280,19 +275,21 @@ int git_indexer_write(git_indexer *idx)
 	git_mwindow_close(&w);
 
 	error = git_filebuf_write(&idx->file, &file_hash, sizeof(git_oid));
+	if (error < 0)
+		goto cleanup;
 
 	/* Write out the index sha */
 	error = git_filebuf_hash(&file_hash, &idx->file);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		goto cleanup;
 
 	error = git_filebuf_write(&idx->file, &file_hash, sizeof(git_oid));
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		goto cleanup;
 
 	/* Figure out what the final name should be */
 	error = index_path(&filename, idx);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		goto cleanup;
 
 	/* Commit file */
@@ -300,7 +297,7 @@ int git_indexer_write(git_indexer *idx)
 
 cleanup:
 	git_mwindow_free_all(&idx->pack->mwf);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		git_filebuf_cleanup(&idx->file);
 	git_buf_free(&filename);
 
@@ -319,8 +316,8 @@ int git_indexer_run(git_indexer *idx, git_indexer_stats *stats)
 
 	mwf = &idx->pack->mwf;
 	error = git_mwindow_file_register(mwf);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to register mwindow file");
+	if (error < 0)
+		return error;
 
 	stats->total = (unsigned int)idx->nr_objects;
 	stats->processed = processed = 0;
@@ -346,27 +343,26 @@ int git_indexer_run(git_indexer *idx, git_indexer_stats *stats)
 		}
 
 		error = git_packfile_unpack(&obj, idx->pack, &off);
-		if (error < GIT_SUCCESS) {
-			error = git__rethrow(error, "Failed to unpack object");
+		if (error < 0)
 			goto cleanup;
-		}
 
 		/* FIXME: Parse the object instead of hashing it */
 		error = git_odb__hashobj(&oid, &obj);
-		if (error < GIT_SUCCESS) {
-			error = git__rethrow(error, "Failed to hash object");
+		if (error < 0) {
+			giterr_set(GITERR_INVALID, "Failed to hash object");
 			goto cleanup;
 		}
 
 		pentry = git__malloc(sizeof(struct git_pack_entry));
 		if (pentry == NULL) {
-			error = GIT_ENOMEM;
+			error = -1;
 			goto cleanup;
 		}
+
 		git_oid_cpy(&pentry->sha1, &oid);
 		pentry->offset = entry_start;
 		error = git_vector_insert(&idx->pack->cache, pentry);
-		if (error < GIT_SUCCESS)
+		if (error < 0)
 			goto cleanup;
 
 		git_oid_cpy(&entry->oid, &oid);
@@ -375,7 +371,7 @@ int git_indexer_run(git_indexer *idx, git_indexer_stats *stats)
 		entry_size = (size_t)(off - entry_start);
 		packed = git_mwindow_open(mwf, &w, entry_start, entry_size, &left);
 		if (packed == NULL) {
-			error = git__rethrow(error, "Failed to open window to read packed data");
+			error = -1;
 			goto cleanup;
 		}
 		entry->crc = htonl(crc32(entry->crc, packed, (uInt)entry_size));
@@ -383,10 +379,8 @@ int git_indexer_run(git_indexer *idx, git_indexer_stats *stats)
 
 		/* Add the object to the list */
 		error = git_vector_insert(&idx->objects, entry);
-		if (error < GIT_SUCCESS) {
-			error = git__rethrow(error, "Failed to add entry to list");
+		if (error < 0)
 			goto cleanup;
-		}
 
 		for (i = oid.id[0]; i < 256; ++i) {
 			idx->fanout[i]++;
diff --git a/src/notes.c b/src/notes.c
index 68554c3..05c70c6 100644
--- a/src/notes.c
+++ b/src/notes.c
@@ -21,11 +21,8 @@ static int find_subtree(git_tree **subtree, const git_oid *root,
 	*subtree = NULL;
 
 	error = git_tree_lookup(&tree, repo, root);
-	if (error < GIT_SUCCESS) {
-		if (error == GIT_ENOTFOUND)
-			return error; /* notes tree doesn't exist yet */
-		return git__rethrow(error, "Failed to open notes tree");
-	}
+	if (error < 0)
+		return error;
 
 	for (i=0; i<git_tree_entrycount(tree); i++) {
 		entry = git_tree_entry_byindex(tree, i);
@@ -56,7 +53,7 @@ static int find_subtree(git_tree **subtree, const git_oid *root,
 	}
 
 	*subtree = tree;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int find_blob(git_oid *blob, git_tree *tree, const char *target)
@@ -71,7 +68,7 @@ static int find_blob(git_oid *blob, git_tree *tree, const char *target)
 			/* found matching note object - return */
 
 			git_oid_cpy(blob, git_tree_entry_id(entry));
-			return GIT_SUCCESS;
+			return 0;
 		}
 	}
 	return GIT_ENOTFOUND;
@@ -93,18 +90,17 @@ static int note_write(git_oid *out, git_repository *repo,
 
 	if (tree_sha) {
 		error = find_subtree(&tree, tree_sha, repo, target, &fanout);
-		if (error < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to lookup subtree");
+		if (error < 0)
+			return error;
 
 		error = find_blob(&oid, tree, target + fanout);
-		if (error < GIT_SUCCESS && error != GIT_ENOTFOUND) {
-			git_tree_free(tree);
-			return git__throw(GIT_ENOTFOUND, "Failed to read subtree %s", target);
-		}
-
-		if (error == GIT_SUCCESS) {
+		if (error != GIT_ENOTFOUND) {
 			git_tree_free(tree);
-			return git__throw(GIT_EEXISTS, "Note for `%s` exists already", target);
+			if (!error) {
+				giterr_set(GITERR_REPOSITORY, "Note for '%s' exists already", target);
+				error = GIT_EEXISTS;
+			}
+			return error;
 		}
 	}
 
@@ -113,8 +109,8 @@ static int note_write(git_oid *out, git_repository *repo,
 	error = git_treebuilder_create(&tb, tree);
 	git_tree_free(tree);
 
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to create treebuilder");
+	if (error < 0)
+		return error;
 
 	if (!tree_sha)
 		/* no notes tree yet - create fanout */
@@ -122,18 +118,18 @@ static int note_write(git_oid *out, git_repository *repo,
 
 	/* create note object */
 	error = git_blob_create_frombuffer(&oid, repo, note, strlen(note));
-	if (error < GIT_SUCCESS) {
+	if (error < 0) {
 		git_treebuilder_free(tb);
-		return git__rethrow(error, "Failed to create note object");
+		return error;
 	}
 
 	error = git_treebuilder_insert(&entry, tb, target + fanout, &oid, 0100644);
-	if (error < GIT_SUCCESS) {
+	if (error < 0) {
 		/* libgit2 doesn't support object removal (gc) yet */
 		/* we leave an orphaned blob object behind - TODO */
 
 		git_treebuilder_free(tb);
-		return git__rethrow(error, "Failed to insert note object");
+		return error;
 	}
 
 	if (out)
@@ -142,8 +138,8 @@ static int note_write(git_oid *out, git_repository *repo,
 	error = git_treebuilder_write(&oid, repo, tb);
 	git_treebuilder_free(tb);
 
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to write notes tree");
+	if (error < 0)
+		return 0;
 
 	if (!tree_sha) {
 		/* create fanout subtree */
@@ -153,27 +149,28 @@ static int note_write(git_oid *out, git_repository *repo,
 		subtree[2] = '\0';
 
 		error = git_treebuilder_create(&tb, NULL);
-		if (error < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to create treebuilder");
+		if (error < 0)
+			return error;
 
 		error = git_treebuilder_insert(NULL, tb, subtree, &oid, 0040000);
-		if (error < GIT_SUCCESS) {
+		if (error < 0) {
 			git_treebuilder_free(tb);
-			return git__rethrow(error, "Failed to insert note object");
+			return error;
 		}
 
 		error = git_treebuilder_write(&oid, repo, tb);
+
 		git_treebuilder_free(tb);
 
-		if (error < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to write notes tree");
+		if (error < 0)
+			return error;
 	}
 
 	/* create new notes commit */
 
 	error = git_tree_lookup(&tree, repo, &oid);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to open new notes tree");
+	if (error < 0)
+		return error;
 
 	error = git_commit_create(&oid, repo, notes_ref, author, committer,
 				  NULL, GIT_NOTES_DEFAULT_MSG_ADD,
@@ -181,10 +178,7 @@ static int note_write(git_oid *out, git_repository *repo,
 
 	git_tree_free(tree);
 
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to create new notes commit");
-
-	return GIT_SUCCESS;
+	return error;
 }
 
 static int note_lookup(git_note **out, git_repository *repo,
@@ -197,31 +191,25 @@ static int note_lookup(git_note **out, git_repository *repo,
 	git_note *note;
 
 	error = find_subtree(&tree, tree_sha, repo, target, &fanout);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to lookup subtree");
+	if (error < 0)
+		return error;
 
 	error = find_blob(&oid, tree, target + fanout);
-	if (error < GIT_SUCCESS) {
-		git_tree_free(tree);
-		return git__throw(GIT_ENOTFOUND, "No note found for object %s",
-				  target);
-	}
+
 	git_tree_free(tree);
+	if (error < 0)
+		return error;
 
 	error = git_blob_lookup(&blob, repo, &oid);
-	if (error < GIT_SUCCESS)
-		return git__throw(GIT_ERROR, "Failed to lookup note object");
+	if (error < 0)
+		return error;
 
 	note = git__malloc(sizeof(git_note));
-	if (note == NULL) {
-		git_blob_free(blob);
-		return GIT_ENOMEM;
-	}
+	GITERR_CHECK_ALLOC(note);
 
 	git_oid_cpy(&note->oid, &oid);
 	note->message = git__strdup(git_blob_rawcontent(blob));
-	if (note->message == NULL)
-		error = GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(note->message);
 
 	*out = note;
 
@@ -240,39 +228,30 @@ static int note_remove(git_repository *repo,
 	git_treebuilder *tb;
 
 	error = find_subtree(&tree, tree_sha, repo, target, &fanout);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to lookup subtree");
+	if (error < 0)
+		return error;
 
 	error = find_blob(&oid, tree, target + fanout);
-	if (error < GIT_SUCCESS) {
-		git_tree_free(tree);
-		return git__throw(GIT_ENOTFOUND, "No note found for object %s",
-				  target);
-	}
+	if (!error)
+		error = git_treebuilder_create(&tb, tree);
 
-	error = git_treebuilder_create(&tb, tree);
 	git_tree_free(tree);
-
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to create treebuilder");
+	if (error < 0)
+		return error;
 
 	error = git_treebuilder_remove(tb, target + fanout);
-	if (error < GIT_SUCCESS) {
-		git_treebuilder_free(tb);
-		return git__rethrow(error, "Failed to remove entry from notes tree");
-	}
+	if (!error)
+		error = git_treebuilder_write(&oid, repo, tb);
 
-	error = git_treebuilder_write(&oid, repo, tb);
 	git_treebuilder_free(tb);
-
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to write notes tree");
+	if (error < 0)
+		return error;
 
 	/* create new notes commit */
 
 	error = git_tree_lookup(&tree, repo, &oid);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to open new notes tree");
+	if (error < 0)
+		return error;
 
 	error = git_commit_create(&oid, repo, notes_ref, author, committer,
 				  NULL, GIT_NOTES_DEFAULT_MSG_RM,
@@ -280,9 +259,6 @@ static int note_remove(git_repository *repo,
 
 	git_tree_free(tree);
 
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to create new notes commit");
-
 	return error;
 }
 
@@ -301,8 +277,8 @@ int git_note_read(git_note **out, git_repository *repo,
 		notes_ref = GIT_NOTES_DEFAULT_REF;
 
 	error = git_reference_lookup(&ref, repo, notes_ref);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to lookup reference `%s`", notes_ref);
+	if (error < 0)
+		return error;
 
 	assert(git_reference_type(ref) == GIT_REF_OID);
 
@@ -311,27 +287,26 @@ int git_note_read(git_note **out, git_repository *repo,
 
 	git_reference_free(ref);
 
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to find notes commit object");
+	if (error < 0)
+		return error;
 
 	sha = git_commit_tree_oid(commit);
 	git_commit_free(commit);
 
 	target = git_oid_allocfmt(oid);
-	if (target == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(target);
 
 	error = note_lookup(out, repo, sha, target);
 
 	git__free(target);
-	return error == GIT_SUCCESS ? GIT_SUCCESS :
-		git__rethrow(error, "Failed to read note");
+	return error;
 }
 
-int git_note_create(git_oid *out, git_repository *repo,
-		    git_signature *author, git_signature *committer,
-		    const char *notes_ref, const git_oid *oid,
-		     const char *note)
+int git_note_create(
+	git_oid *out, git_repository *repo,
+	git_signature *author, git_signature *committer,
+	const char *notes_ref, const git_oid *oid,
+	const char *note)
 {
 	int error, nparents = 0;
 	char *target;
@@ -343,10 +318,10 @@ int git_note_create(git_oid *out, git_repository *repo,
 		notes_ref = GIT_NOTES_DEFAULT_REF;
 
 	error = git_reference_lookup(&ref, repo, notes_ref);
-	if (error < GIT_SUCCESS && error != GIT_ENOTFOUND)
-		return git__rethrow(error, "Failed to lookup reference `%s`", notes_ref);
+	if (error < 0 && error != GIT_ENOTFOUND)
+		return error;
 
-	if (error == GIT_SUCCESS) {
+	if (!error) {
 		assert(git_reference_type(ref) == GIT_REF_OID);
 
 		/* lookup existing notes tree oid */
@@ -355,16 +330,15 @@ int git_note_create(git_oid *out, git_repository *repo,
 		git_reference_free(ref);
 
 		error = git_commit_lookup(&commit, repo, &sha);
-		if (error < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to find notes commit object");
+		if (error < 0)
+			return error;
 
 		git_oid_cpy(&sha, git_commit_tree_oid(commit));
 		nparents++;
 	}
 
 	target = git_oid_allocfmt(oid);
-	if (target == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(target);
 
 	error = note_write(out, repo, author, committer, notes_ref,
 			   note, nparents ? &sha : NULL, target,
@@ -372,8 +346,7 @@ int git_note_create(git_oid *out, git_repository *repo,
 
 	git__free(target);
 	git_commit_free(commit);
-	return error == GIT_SUCCESS ? GIT_SUCCESS :
-		git__rethrow(error, "Failed to write note");
+	return error;
 }
 
 int git_note_remove(git_repository *repo, const char *notes_ref,
@@ -390,8 +363,8 @@ int git_note_remove(git_repository *repo, const char *notes_ref,
 		notes_ref = GIT_NOTES_DEFAULT_REF;
 
 	error = git_reference_lookup(&ref, repo, notes_ref);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to lookup reference `%s`", notes_ref);
+	if (error < 0)
+		return error;
 
 	assert(git_reference_type(ref) == GIT_REF_OID);
 
@@ -399,22 +372,20 @@ int git_note_remove(git_repository *repo, const char *notes_ref,
 	git_reference_free(ref);
 
 	error = git_commit_lookup(&commit, repo, &sha);
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to find notes commit object");
+	if (error < 0)
+		return error;
 
 	git_oid_cpy(&sha, git_commit_tree_oid(commit));
 
 	target = git_oid_allocfmt(oid);
-	if (target == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(target);
 
 	error = note_remove(repo, author, committer, notes_ref,
 			    &sha, target, 1, &commit);
 
 	git__free(target);
 	git_commit_free(commit);
-	return error == GIT_SUCCESS ? GIT_SUCCESS :
-		git__rethrow(error, "Failed to read note");
+	return error;
 }
 
 const char * git_note_message(git_note *note)
diff --git a/src/odb.c b/src/odb.c
index f68d135..b615cc4 100644
--- a/src/odb.c
+++ b/src/odb.c
@@ -541,6 +541,10 @@ int git_odb_read(git_odb_object **out, git_odb *db, const git_oid *id)
 			error = b->read(&raw.data, &raw.len, &raw.type, b, id);
 	}
 
+	/* TODO: If no backends are configured, this returns GIT_ENOTFOUND but
+	 * will never have called giterr_set().
+	 */
+
 	if (error && error != GIT_EPASSTHROUGH)
 		return error;
 
diff --git a/src/sha1_lookup.c b/src/sha1_lookup.c
index 58d70ae..096da17 100644
--- a/src/sha1_lookup.c
+++ b/src/sha1_lookup.c
@@ -158,7 +158,8 @@ int sha1_entry_pos(const void *table,
 #endif
 
 		if (!(lo <= mi && mi < hi)) {
-			return git__throw(GIT_ERROR, "Assertion failure. Binary search invariant is false");
+			giterr_set(GITERR_INVALID, "Assertion failure. Binary search invariant is false");
+			return -1;
 		}
 
 		mi_key = base + elem_size * mi + key_offset;
diff --git a/src/signature.c b/src/signature.c
index 1b6ba21..6aaab4f 100644
--- a/src/signature.c
+++ b/src/signature.c
@@ -38,31 +38,38 @@ static const char *skip_trailing_spaces(const char *buffer_start, const char *bu
 	return buffer_end;
 }
 
+static int signature_error(const char *msg)
+{
+	giterr_set(GITERR_INVALID, "Failed to parse signature - %s", msg);
+	return -1;
+}
+
 static int process_trimming(const char *input, char **storage, const char *input_end, int fail_when_empty)
 {
 	const char *left, *right;
 	int trimmed_input_length;
 
+	assert(storage);
+
 	left = skip_leading_spaces(input, input_end);
 	right = skip_trailing_spaces(input, input_end - 1);
 
 	if (right < left) {
 		if (fail_when_empty)
-			return git__throw(GIT_EINVALIDARGS, "Failed to trim. Input is either empty or only contains spaces");
-		else
-			right = left - 1;
+			return signature_error("input is either empty of contains only spaces");
+
+		right = left - 1;
 	}
 
 	trimmed_input_length = right - left + 1;
 
 	*storage = git__malloc(trimmed_input_length + 1);
-	if (*storage == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(*storage);
 
 	memcpy(*storage, left, trimmed_input_length);
 	(*storage)[trimmed_input_length] = 0;
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 int git_signature_new(git_signature **sig_out, const char *name, const char *email, git_time_t time, int offset)
@@ -74,23 +81,14 @@ int git_signature_new(git_signature **sig_out, const char *name, const char *ema
 
 	*sig_out = NULL;
 
-	if ((p = git__malloc(sizeof(git_signature))) == NULL) {
-		error = GIT_ENOMEM;
-		goto cleanup;
-	}
-
-	memset(p, 0x0, sizeof(git_signature));
-
-	error = process_trimming(name, &p->name, name + strlen(name), 1);
-	if (error < GIT_SUCCESS) {
-		git__rethrow(GIT_EINVALIDARGS, "Failed to create signature. 'name' argument is invalid");
-		goto cleanup;
-	}
+	p = git__calloc(1, sizeof(git_signature));
+	GITERR_CHECK_ALLOC(p);
 
-	error = process_trimming(email, &p->email, email + strlen(email), 1);
-	if (error < GIT_SUCCESS) {
-		git__rethrow(GIT_EINVALIDARGS, "Failed to create signature. 'email' argument is invalid");
-		goto cleanup;
+	if ((error = process_trimming(name, &p->name, name + strlen(name), 1)) < 0 ||
+		(error = process_trimming(email, &p->email, email + strlen(email), 1)) < 0)
+	{
+		git_signature_free(p);
+		return error;
 	}
 
 	p->when.time = time;
@@ -98,24 +96,19 @@ int git_signature_new(git_signature **sig_out, const char *name, const char *ema
 
 	*sig_out = p;
 
-	return error;
-
-cleanup:
-	git_signature_free(p);
-	return error;
+	return 0;
 }
 
 git_signature *git_signature_dup(const git_signature *sig)
 {
 	git_signature *new;
-	if (git_signature_new(&new, sig->name, sig->email, sig->when.time, sig->when.offset) < GIT_SUCCESS)
+	if (git_signature_new(&new, sig->name, sig->email, sig->when.time, sig->when.offset) < 0)
 		return NULL;
 	return new;
 }
 
 int git_signature_now(git_signature **sig_out, const char *name, const char *email)
 {
-	int error;
 	time_t now;
 	time_t offset;
 	struct tm *utc_tm, *local_tm;
@@ -148,12 +141,18 @@ int git_signature_now(git_signature **sig_out, const char *name, const char *ema
 	if (local_tm->tm_isdst)
 		offset += 60;
 
-	if ((error = git_signature_new(&sig, name, email, now, (int)offset)) < GIT_SUCCESS)
-		return error;
+	if (git_signature_new(&sig, name, email, now, (int)offset) < 0)
+		return -1;
 
 	*sig_out = sig;
 
-	return error;
+	return 0;
+}
+
+static int timezone_error(const char *msg)
+{
+	giterr_set(GITERR_INVALID, "Failed to parse TZ offset - %s", msg);
+	return -1;
 }
 
 static int parse_timezone_offset(const char *buffer, int *offset_out)
@@ -172,28 +171,28 @@ static int parse_timezone_offset(const char *buffer, int *offset_out)
 	}
 
 	if (offset_start[0] != '-' && offset_start[0] != '+')
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse TZ offset. It doesn't start with '+' or '-'");
+		return timezone_error("does not start with '+' or '-'");
 
 	if (offset_start[1] < '0' || offset_start[1] > '9')
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse TZ offset.");
+		return timezone_error("expected initial digit");
 
 	if (git__strtol32(&dec_offset, offset_start + 1, &offset_end, 10) < GIT_SUCCESS)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse TZ offset. It isn't a number");
+		return timezone_error("not a valid number");
 
 	if (offset_end - offset_start != 5)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse TZ offset. Invalid length");
+		return timezone_error("invalid length");
 
 	if (dec_offset > 1400)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse TZ offset. Value too large");
+		return timezone_error("value too large");
 
 	hours = dec_offset / 100;
 	mins = dec_offset % 100;
 
 	if (hours > 14)	// see http://www.worldtimezone.com/faq.html
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse TZ offset. Hour value too large");
+		return timezone_error("hour value too large");
 
 	if (mins > 59)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse TZ offset. Minute value too large");
+		return timezone_error("minutes value too large");
 
 	offset = (hours * 60) + mins;
 
@@ -202,22 +201,22 @@ static int parse_timezone_offset(const char *buffer, int *offset_out)
 
 	*offset_out = offset;
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int process_next_token(const char **buffer_out, char **storage,
 	const char *token_end, const char *right_boundary)
 {
 	int error = process_trimming(*buffer_out, storage, token_end, 0);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		return error;
 
 	*buffer_out = token_end + 1;
 
 	if (*buffer_out > right_boundary)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. Signature too short");
+		return signature_error("signature is too short");
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static const char *scan_for_previous_token(const char *buffer, const char *left_boundary)
@@ -241,17 +240,17 @@ static int parse_time(git_time_t *time_out, const char *buffer)
 	int time;
 	int error;
 
-	if (*buffer == '+' || *buffer == '-')
-		return git__throw(GIT_ERROR, "Failed while parsing time. '%s' rather look like a timezone offset.", buffer);
+	if (*buffer == '+' || *buffer == '-') {
+		giterr_set(GITERR_INVALID, "Failed while parsing time. '%s' actually looks like a timezone offset.", buffer);
+		return -1;
+	}
 
 	error = git__strtol32(&time, buffer, &buffer, 10);
 
-	if (error < GIT_SUCCESS)
-		return error;
+	if (!error)
+		*time_out = (git_time_t)time;
 
-	*time_out = (git_time_t)time;
-
-	return GIT_SUCCESS;
+	return error;
 }
 
 int git_signature__parse(git_signature *sig, const char **buffer_out,
@@ -264,35 +263,35 @@ int git_signature__parse(git_signature *sig, const char **buffer_out,
 	memset(sig, 0x0, sizeof(git_signature));
 
 	if ((line_end = memchr(buffer, ender, buffer_end - buffer)) == NULL)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. No newline given");
+		return signature_error("no newline given");
 
 	if (header) {
 		const size_t header_len = strlen(header);
 
 		if (memcmp(buffer, header, header_len) != 0)
-			return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. Expected prefix '%s' doesn't match actual", header);
+			return signature_error("expected prefix doesn't match actual");
 
 		buffer += header_len;
 	}
 
 	if (buffer > line_end)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. Signature too short");
+		return signature_error("signature too short");
 
 	if ((name_end = strchr(buffer, '<')) == NULL)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. Cannot find '<' in signature");
+		return signature_error("character '<' not allowed in signature");
 
 	if ((email_end = strchr(name_end, '>')) == NULL)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. Cannot find '>' in signature");
+		return signature_error("character '>' not allowed in signature");
 
 	if (email_end < name_end)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse signature. Malformed e-mail");
+		return signature_error("malformed e-mail");
 
 	error = process_next_token(&buffer, &sig->name, name_end, line_end);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		return error;
 
 	error = process_next_token(&buffer, &sig->email, email_end, line_end);
-	if (error < GIT_SUCCESS)
+	if (error < 0)
 		return error;
 
 	tz_start = scan_for_previous_token(line_end - 1, buffer);
@@ -301,19 +300,19 @@ int git_signature__parse(git_signature *sig, const char **buffer_out,
 		goto clean_exit;	/* No timezone nor date */
 
 	time_start = scan_for_previous_token(tz_start - 1, buffer);
-	if (time_start == NULL || parse_time(&sig->when.time, time_start) < GIT_SUCCESS) {
+	if (time_start == NULL || parse_time(&sig->when.time, time_start) < 0) {
 		/* The tz_start might point at the time */
 		parse_time(&sig->when.time, tz_start);
 		goto clean_exit;
 	}
 
-	if (parse_timezone_offset(tz_start, &sig->when.offset) < GIT_SUCCESS) {
+	if (parse_timezone_offset(tz_start, &sig->when.offset) < 0) {
 		sig->when.time = 0; /* Bogus timezone, we reset the time */
 	}
 
 clean_exit:
 	*buffer_out = line_end + 1;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 void git_signature__writebuf(git_buf *buf, const char *header, const git_signature *sig)