thodg/libgit2

diff --git a/include/git2.h b/include/git2.h
index 7d053c4..d753873 100644
--- a/include/git2.h
+++ b/include/git2.h
@@ -22,6 +22,7 @@
 
 #include "git2/repository.h"
 #include "git2/revwalk.h"
+#include "git2/merge.h"
 #include "git2/refs.h"
 #include "git2/reflog.h"
 
diff --git a/include/git2/merge.h b/include/git2/merge.h
new file mode 100644
index 0000000..5a0b2e7
--- /dev/null
+++ b/include/git2/merge.h
@@ -0,0 +1,35 @@
+/*
+ * Copyright (C) 2009-2012 the libgit2 contributors
+ *
+ * This file is part of libgit2, distributed under the GNU GPL v2 with
+ * a Linking Exception. For full terms see the included COPYING file.
+ */
+#ifndef INCLUDE_git_merge_h__
+#define INCLUDE_git_merge_h__
+
+#include "common.h"
+#include "types.h"
+#include "oid.h"
+
+/**
+ * @file git2/merge.h
+ * @brief Git merge-base routines
+ * @defgroup git_revwalk Git merge-base routines
+ * @ingroup Git
+ * @{
+ */
+GIT_BEGIN_DECL
+
+/**
+ * Find a merge base between two commits
+ *
+ * @param out the OID of a merge base between 'one' and 'two'
+ * @param repo the repository where the commits exist
+ * @param one one of the commits
+ * @param two the other commit
+ */
+GIT_EXTERN(int) git_merge_base(git_oid *out, git_repository *repo, git_oid *one, git_oid *two);
+
+/** @} */
+GIT_END_DECL
+#endif
diff --git a/include/git2/revwalk.h b/include/git2/revwalk.h
index e7ec2ab..632c675 100644
--- a/include/git2/revwalk.h
+++ b/include/git2/revwalk.h
@@ -164,6 +164,28 @@ GIT_EXTERN(int) git_revwalk_hide_glob(git_revwalk *walk, const char *glob);
 GIT_EXTERN(int) git_revwalk_hide_head(git_revwalk *walk);
 
 /**
+ * Push the OID pointed to by a reference
+ *
+ * The reference must point to a commit.
+ *
+ * @param walk the walker being used for the traversal
+ * @param refname the referece to push
+ * @return GIT_SUCCESS or an error code
+ */
+GIT_EXTERN(int) git_revwalk_push_ref(git_revwalk *walk, const char *refname);
+
+/**
+ * Hide the OID pointed to by a reference
+ *
+ * The reference must point to a commit.
+ *
+ * @param walk the walker being used for the traversal
+ * @param refname the referece to hide
+ * @return GIT_SUCCESS or an error code
+ */
+GIT_EXTERN(int) git_revwalk_hide_ref(git_revwalk *walk, const char *refname);
+
+/**
  * Get the next commit from the revision walk.
  *
  * The initial call to this method is *not* blocking when
diff --git a/src/revwalk.c b/src/revwalk.c
index 997771f..c2c098c 100644
--- a/src/revwalk.c
+++ b/src/revwalk.c
@@ -12,16 +12,23 @@
 #include "pqueue.h"
 
 #include "git2/revwalk.h"
+#include "git2/merge.h"
 
 #include <regex.h>
 
+#define PARENT1  (1 << 0)
+#define PARENT2  (1 << 1)
+#define RESULT   (1 << 2)
+#define STALE    (1 << 3)
+
 typedef struct commit_object {
 	git_oid oid;
 	uint32_t time;
 	unsigned int seen:1,
 			 uninteresting:1,
 			 topo_delay:1,
-			 parsed:1;
+			 parsed:1,
+			 flags : 4;
 
 	unsigned short in_degree;
 	unsigned short out_degree;
@@ -53,17 +60,46 @@ struct git_revwalk {
 
 	unsigned walking:1;
 	unsigned int sorting;
+
+	/* merge base calculation */
+	commit_object *one;
+	git_vector twos;
 };
 
+static int commit_time_cmp(void *a, void *b)
+{
+	commit_object *commit_a = (commit_object *)a;
+	commit_object *commit_b = (commit_object *)b;
+
+	return (commit_a->time < commit_b->time);
+}
+
 static commit_list *commit_list_insert(commit_object *item, commit_list **list_p)
 {
 	commit_list *new_list = git__malloc(sizeof(commit_list));
+	if (new_list == NULL)
+		return NULL;
+
 	new_list->item = item;
 	new_list->next = *list_p;
 	*list_p = new_list;
 	return new_list;
 }
 
+static commit_list *commit_list_insert_by_date(commit_object *item, commit_list **list_p)
+{
+	commit_list **pp = list_p;
+	commit_list *p;
+
+	while ((p = *pp) != NULL) {
+		if (commit_time_cmp(p->item, item) < 0)
+			break;
+
+		pp = &p->next;
+	}
+
+	return commit_list_insert(item, pp);
+}
 static void commit_list_free(commit_list **list_p)
 {
 	commit_list *list = *list_p;
@@ -89,14 +125,6 @@ static commit_object *commit_list_pop(commit_list **stack)
 	return item;
 }
 
-static int commit_time_cmp(void *a, void *b)
-{
-	commit_object *commit_a = (commit_object *)a;
-	commit_object *commit_b = (commit_object *)b;
-
-	return (commit_a->time < commit_b->time);
-}
-
 static uint32_t object_table_hash(const void *key, int hash_id)
 {
 	uint32_t r;
@@ -186,38 +214,43 @@ static int commit_quick_parse(git_revwalk *walk, commit_object *commit, git_rawo
 	}
 
 	commit->parents = alloc_parents(commit, parents);
-	if (commit->parents == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(commit->parents);
 
 	buffer = parents_start;
 	for (i = 0; i < parents; ++i) {
 		git_oid oid;
 
-		if (git_oid_fromstr(&oid, (char *)buffer + strlen("parent ")) < GIT_SUCCESS)
-			return git__throw(GIT_EOBJCORRUPTED, "Failed to parse commit. Parent object is corrupted");
+		if (git_oid_fromstr(&oid, (char *)buffer + strlen("parent ")) < 0)
+			return -1;
 
 		commit->parents[i] = commit_lookup(walk, &oid);
 		if (commit->parents[i] == NULL)
-			return GIT_ENOMEM;
+			return -1;
 
 		buffer += parent_len;
 	}
 
 	commit->out_degree = (unsigned short)parents;
 
-	if ((buffer = memchr(buffer, '\n', buffer_end - buffer)) == NULL)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse commit. Object is corrupted");
+	if ((buffer = memchr(buffer, '\n', buffer_end - buffer)) == NULL) {
+		giterr_set(GITERR_ODB, "Failed to parse commit. Object is corrupted");
+		return -1;
+	}
 
 	buffer = memchr(buffer, '>', buffer_end - buffer);
-	if (buffer == NULL)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse commit. Can't find author");
+	if (buffer == NULL) {
+		giterr_set(GITERR_ODB, "Failed to parse commit. Can't find author");
+		return -1;
+	}
 
-	if (git__strtol32(&commit_time, (char *)buffer + 2, NULL, 10) < GIT_SUCCESS)
-		return git__throw(GIT_EOBJCORRUPTED, "Failed to parse commit. Can't parse commit time");
+	if (git__strtol32(&commit_time, (char *)buffer + 2, NULL, 10) < 0) {
+		giterr_set(GITERR_ODB, "Failed to parse commit. Can't parse commit time");
+		return -1;
+	}
 
 	commit->time = (time_t)commit_time;
 	commit->parsed = 1;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int commit_parse(git_revwalk *walk, commit_object *commit)
@@ -226,19 +259,159 @@ static int commit_parse(git_revwalk *walk, commit_object *commit)
 	int error;
 
 	if (commit->parsed)
-		return GIT_SUCCESS;
+		return 0;
 
-	if ((error = git_odb_read(&obj, walk->odb, &commit->oid)) < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to parse commit. Can't read object");
+	if ((error = git_odb_read(&obj, walk->odb, &commit->oid)) < 0)
+		return -1;
 
 	if (obj->raw.type != GIT_OBJ_COMMIT) {
 		git_odb_object_free(obj);
-		return git__throw(GIT_EOBJTYPE, "Failed to parse commit. Object is no commit object");
+		giterr_set(GITERR_INVALID, "Failed to parse commit. Object is no commit object");
+		return -1;
 	}
 
 	error = commit_quick_parse(walk, commit, &obj->raw);
 	git_odb_object_free(obj);
-	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to parse commit");
+	return error;
+}
+
+static int interesting(git_pqueue *list)
+{
+	unsigned int i;
+	for (i = 1; i < git_pqueue_size(list); i++) {
+		commit_object *commit = list->d[i];
+		if ((commit->flags & STALE) == 0)
+			return 1;
+	}
+
+	return 0;
+}
+
+static int merge_bases_many(commit_list **out, git_revwalk *walk, commit_object *one, git_vector *twos)
+{
+	int error;
+	unsigned int i;
+	commit_object *two;
+	commit_list *result = NULL, *tmp = NULL;
+	git_pqueue list;
+
+	/* if the commit is repeated, we have a our merge base already */
+	git_vector_foreach(twos, i, two) {
+		if (one == two)
+			return commit_list_insert(one, out) ? 0 : -1;
+	}
+
+	if (git_pqueue_init(&list, twos->length * 2, commit_time_cmp) < 0)
+		return -1;
+
+	if (commit_parse(walk, one) < 0)
+	    return -1;
+
+	one->flags |= PARENT1;
+	if (git_pqueue_insert(&list, one) < 0)
+		return -1;
+
+	git_vector_foreach(twos, i, two) {
+		commit_parse(walk, two);
+		two->flags |= PARENT2;
+		if (git_pqueue_insert(&list, two) < 0)
+			return -1;
+	}
+
+	/* as long as there are non-STALE commits */
+	while (interesting(&list)) {
+		commit_object *commit;
+		int flags;
+
+		commit = git_pqueue_pop(&list);
+
+		flags = commit->flags & (PARENT1 | PARENT2 | STALE);
+		if (flags == (PARENT1 | PARENT2)) {
+			if (!(commit->flags & RESULT)) {
+				commit->flags |= RESULT;
+				if (commit_list_insert(commit, &result) == NULL)
+					return -1;
+			}
+			/* we mark the parents of a merge stale */
+			flags |= STALE;
+		}
+
+		for (i = 0; i < commit->out_degree; i++) {
+			commit_object *p = commit->parents[i];
+			if ((p->flags & flags) == flags)
+				continue;
+
+			if ((error = commit_parse(walk, p)) < GIT_SUCCESS)
+				return error;
+
+			p->flags |= flags;
+			if (git_pqueue_insert(&list, p) < 0)
+				return -1;
+		}
+	}
+
+	git_pqueue_free(&list);
+
+	/* filter out any stale commits in the results */
+	tmp = result;
+	result = NULL;
+
+	while (tmp) {
+		struct commit_list *next = tmp->next;
+		if (!(tmp->item->flags & STALE))
+			if (commit_list_insert_by_date(tmp->item, &result) == NULL)
+				return -1;
+
+		git__free(tmp);
+		tmp = next;
+	}
+
+	*out = result;
+	return 0;
+}
+
+int git_merge_base(git_oid *out, git_repository *repo, git_oid *one, git_oid *two)
+{
+	git_revwalk *walk;
+	git_vector list;
+	commit_list *result = NULL;
+	commit_object *commit;
+	void *contents[1];
+
+	if (git_revwalk_new(&walk, repo) < 0)
+		return -1;
+
+	commit = commit_lookup(walk, two);
+	if (commit == NULL)
+		goto on_error;
+
+	/* This is just one value, so we can do it on the stack */
+	memset(&list, 0x0, sizeof(git_vector));
+	contents[0] = commit;
+	list.length = 1;
+	list.contents = contents;
+
+	commit = commit_lookup(walk, one);
+	if (commit == NULL)
+		goto on_error;
+
+	if (merge_bases_many(&result, walk, commit, &list) < 0)
+		goto on_error;
+
+	if (!result) {
+		git_revwalk_free(walk);
+		return GIT_ENOTFOUND;
+	}
+
+	git_oid_cpy(out, &result->item->oid);
+	commit_list_free(&result);
+	git_revwalk_free(walk);
+
+	return 0;
+
+on_error:
+	git_revwalk_free(walk);
+	return -1;
 }
 
 static void mark_uninteresting(commit_object *commit)
@@ -248,6 +421,10 @@ static void mark_uninteresting(commit_object *commit)
 
 	commit->uninteresting = 1;
 
+	/* This means we've reached a merge base, so there's no need to walk any more */
+	if ((commit->flags & (RESULT | STALE)) == RESULT)
+		return;
+
 	for (i = 0; i < commit->out_degree; ++i)
 		if (!commit->parents[i]->uninteresting)
 			mark_uninteresting(commit->parents[i]);
@@ -255,18 +432,16 @@ static void mark_uninteresting(commit_object *commit)
 
 static int process_commit(git_revwalk *walk, commit_object *commit, int hide)
 {
-	int error;
-
 	if (hide)
 		mark_uninteresting(commit);
 
 	if (commit->seen)
-		return GIT_SUCCESS;
+		return 0;
 
 	commit->seen = 1;
 
-	if ((error = commit_parse(walk, commit)) < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to process commit");
+	if (commit_parse(walk, commit) < 0)
+		return -1;
 
 	return walk->enqueue(walk, commit);
 }
@@ -274,13 +449,13 @@ static int process_commit(git_revwalk *walk, commit_object *commit, int hide)
 static int process_commit_parents(git_revwalk *walk, commit_object *commit)
 {
 	unsigned short i;
-	int error = GIT_SUCCESS;
 
-	for (i = 0; i < commit->out_degree && error == GIT_SUCCESS; ++i) {
-		error = process_commit(walk, commit->parents[i], commit->uninteresting);
+	for (i = 0; i < commit->out_degree; ++i) {
+		if (process_commit(walk, commit->parents[i], commit->uninteresting) < 0)
+			return -1;
 	}
 
-	return error == GIT_SUCCESS ? GIT_SUCCESS : git__rethrow(error, "Failed to process commit parents");
+	return 0;
 }
 
 static int push_commit(git_revwalk *walk, const git_oid *oid, int uninteresting)
@@ -289,9 +464,17 @@ static int push_commit(git_revwalk *walk, const git_oid *oid, int uninteresting)
 
 	commit = commit_lookup(walk, oid);
 	if (commit == NULL)
-		return git__throw(GIT_ENOTFOUND, "Failed to push commit. Object not found");
+		return -1;
 
-	return process_commit(walk, commit, uninteresting);
+	commit->uninteresting = uninteresting;
+	if (walk->one == NULL && !uninteresting) {
+		walk->one = commit;
+	} else {
+		if (git_vector_insert(&walk->twos, commit) < 0)
+			return -1;
+	}
+
+	return 0;
 }
 
 int git_revwalk_push(git_revwalk *walk, const git_oid *oid)
@@ -307,6 +490,25 @@ int git_revwalk_hide(git_revwalk *walk, const git_oid *oid)
 	return push_commit(walk, oid, 1);
 }
 
+static int push_ref(git_revwalk *walk, const char *refname, int hide)
+{
+	git_reference *ref, *resolved;
+	int error;
+
+	if (git_reference_lookup(&ref, walk->repo, refname) < 0)
+		return -1;
+
+	error = git_reference_resolve(&resolved, ref);
+	git_reference_free(ref);
+	if (error < 0)
+		return -1;
+
+	error = push_commit(walk, git_reference_oid(resolved), hide);
+	git_reference_free(resolved);
+
+	return error;
+}
+
 struct push_cb_data {
 	git_revwalk *walk;
 	const char *glob;
@@ -317,30 +519,16 @@ static int push_glob_cb(const char *refname, void *data_)
 {
 	struct push_cb_data *data = (struct push_cb_data *)data_;
 
-	if (!git__fnmatch(data->glob, refname, 0)) {
-		git_reference *ref, *resolved;
-		int error;
-
-		error = git_reference_lookup(&ref, data->walk->repo, refname);
-		if (error < GIT_SUCCESS)
-			return error;
-		error = git_reference_resolve(&resolved, ref);
-		git_reference_free(ref);
-		if (error < GIT_SUCCESS)
-			return error;
-		error = push_commit(data->walk, git_reference_oid(resolved), data->hide);
-		git_reference_free(resolved);
-		return error;
-	}
+	if (!git__fnmatch(data->glob, refname, 0))
+		return push_ref(data->walk, refname, data->hide);
 
-	return GIT_SUCCESS;
+	return 0;
 }
 
 static int push_glob(git_revwalk *walk, const char *glob, int hide)
 {
 	git_buf buf = GIT_BUF_INIT;
 	struct push_cb_data data;
-	int error;
 	regex_t preg;
 
 	assert(walk && glob);
@@ -355,28 +543,32 @@ static int push_glob(git_revwalk *walk, const char *glob, int hide)
 	/* If no '?', '*' or '[' exist, we append '/ *' to the glob */
 	memset(&preg, 0x0, sizeof(regex_t));
 	if (regcomp(&preg, "[?*[]", REG_EXTENDED)) {
-		error = git__throw(GIT_EOSERR, "Regex failed to compile");
-		goto cleanup;
+		giterr_set(GITERR_OS, "Regex failed to compile");
+		git_buf_free(&buf);
+		return -1;
 	}
 
 	if (regexec(&preg, glob, 0, NULL, 0))
 		git_buf_puts(&buf, "/*");
 
-	if (git_buf_oom(&buf)) {
-		error = GIT_ENOMEM;
-		goto cleanup;
-	}
+	if (git_buf_oom(&buf))
+		goto on_error;
 
 	data.walk = walk;
 	data.glob = git_buf_cstr(&buf);
 	data.hide = hide;
 
-	error = git_reference_foreach(walk->repo, GIT_REF_LISTALL, push_glob_cb, &data);
+	if (git_reference_foreach(walk->repo, GIT_REF_LISTALL, push_glob_cb, &data) < 0)
+		goto on_error;
 
-cleanup:
 	regfree(&preg);
 	git_buf_free(&buf);
-	return error;
+	return 0;
+
+on_error:
+	regfree(&preg);
+	git_buf_free(&buf);
+	return -1;
 }
 
 int git_revwalk_push_glob(git_revwalk *walk, const char *glob)
@@ -391,37 +583,28 @@ int git_revwalk_hide_glob(git_revwalk *walk, const char *glob)
 	return push_glob(walk, glob, 1);
 }
 
-static int push_head(git_revwalk *walk, int hide)
-{
-	git_reference *ref, *resolved;
-	int error;
-
-	error = git_reference_lookup(&ref, walk->repo, "HEAD");
-	if (error < GIT_SUCCESS) {
-		return error;
-	}
-	error = git_reference_resolve(&resolved, ref);
-	if (error < GIT_SUCCESS) {
-		return error;
-	}
-	git_reference_free(ref);
-
-	error  = push_commit(walk, git_reference_oid(resolved), hide);
-
-	git_reference_free(resolved);
-	return error;
-}
-
 int git_revwalk_push_head(git_revwalk *walk)
 {
 	assert(walk);
-	return push_head(walk, 0);
+	return push_ref(walk, GIT_HEAD_FILE, 0);
 }
 
 int git_revwalk_hide_head(git_revwalk *walk)
 {
 	assert(walk);
-	return push_head(walk, 1);
+	return push_ref(walk, GIT_HEAD_FILE, 1);
+}
+
+int git_revwalk_push_ref(git_revwalk *walk, const char *refname)
+{
+	assert(walk && refname);
+	return push_ref(walk, refname, 0);
+}
+
+int git_revwalk_hide_ref(git_revwalk *walk, const char *refname)
+{
+	assert(walk && refname);
+	return push_ref(walk, refname, 1);
 }
 
 static int revwalk_enqueue_timesort(git_revwalk *walk, commit_object *commit)
@@ -440,16 +623,16 @@ static int revwalk_next_timesort(commit_object **object_out, git_revwalk *walk)
 	commit_object *next;
 
 	while ((next = git_pqueue_pop(&walk->iterator_time)) != NULL) {
-		if ((error = process_commit_parents(walk, next)) < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to load next revision");
+		if ((error = process_commit_parents(walk, next)) < 0)
+			return -1;
 
 		if (!next->uninteresting) {
 			*object_out = next;
-			return GIT_SUCCESS;
+			return 0;
 		}
 	}
 
-	return git__throw(GIT_EREVWALKOVER, "Failed to load next revision");
+	return GIT_EREVWALKOVER;
 }
 
 static int revwalk_next_unsorted(commit_object **object_out, git_revwalk *walk)
@@ -458,16 +641,16 @@ static int revwalk_next_unsorted(commit_object **object_out, git_revwalk *walk)
 	commit_object *next;
 
 	while ((next = commit_list_pop(&walk->iterator_rand)) != NULL) {
-		if ((error = process_commit_parents(walk, next)) < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to load next revision");
+		if ((error = process_commit_parents(walk, next)) < 0)
+			return -1;
 
 		if (!next->uninteresting) {
 			*object_out = next;
-			return GIT_SUCCESS;
+			return 0;
 		}
 	}
 
-	return git__throw(GIT_EREVWALKOVER, "Failed to load next revision");
+	return GIT_EREVWALKOVER;
 }
 
 static int revwalk_next_toposort(commit_object **object_out, git_revwalk *walk)
@@ -478,7 +661,7 @@ static int revwalk_next_toposort(commit_object **object_out, git_revwalk *walk)
 	for (;;) {
 		next = commit_list_pop(&walk->iterator_topo);
 		if (next == NULL)
-			return git__throw(GIT_EREVWALKOVER, "Failed to load next revision");
+			return GIT_EREVWALKOVER;
 
 		if (next->in_degree > 0) {
 			next->topo_delay = 1;
@@ -490,41 +673,58 @@ static int revwalk_next_toposort(commit_object **object_out, git_revwalk *walk)
 
 			if (--parent->in_degree == 0 && parent->topo_delay) {
 				parent->topo_delay = 0;
-				commit_list_insert(parent, &walk->iterator_topo);
+				if (commit_list_insert(parent, &walk->iterator_topo) == NULL)
+					return -1;
 			}
 		}
 
 		*object_out = next;
-		return GIT_SUCCESS;
+		return 0;
 	}
 }
 
 static int revwalk_next_reverse(commit_object **object_out, git_revwalk *walk)
 {
 	*object_out = commit_list_pop(&walk->iterator_reverse);
-	return *object_out ? GIT_SUCCESS : GIT_EREVWALKOVER;
+	return *object_out ? 0 : GIT_EREVWALKOVER;
 }
 
 
 static int prepare_walk(git_revwalk *walk)
 {
 	int error;
-	commit_object *next;
+	unsigned int i;
+	commit_object *next, *two;
+	commit_list *bases = NULL;
+
+	/* first figure out what the merge bases are */
+	if (merge_bases_many(&bases, walk, walk->one, &walk->twos) < 0)
+		return -1;
+
+	commit_list_free(&bases);
+	if (process_commit(walk, walk->one, walk->one->uninteresting) < 0)
+		return -1;
+
+	git_vector_foreach(&walk->twos, i, two) {
+		if (process_commit(walk, two, two->uninteresting) < 0)
+			return -1;
+	}
 
 	if (walk->sorting & GIT_SORT_TOPOLOGICAL) {
 		unsigned short i;
 
-		while ((error = walk->get_next(&next, walk)) == GIT_SUCCESS) {
+		while ((error = walk->get_next(&next, walk)) == 0) {
 			for (i = 0; i < next->out_degree; ++i) {
 				commit_object *parent = next->parents[i];
 				parent->in_degree++;
 			}
 
-			commit_list_insert(next, &walk->iterator_topo);
+			if (commit_list_insert(next, &walk->iterator_topo) == NULL)
+				return -1;
 		}
 
 		if (error != GIT_EREVWALKOVER)
-			return git__rethrow(error, "Failed to prepare revision walk");
+			return -1;
 
 		walk->get_next = &revwalk_next_toposort;
 	}
@@ -532,16 +732,17 @@ static int prepare_walk(git_revwalk *walk)
 	if (walk->sorting & GIT_SORT_REVERSE) {
 
 		while ((error = walk->get_next(&next, walk)) == GIT_SUCCESS)
-			commit_list_insert(next, &walk->iterator_reverse);
+			if (commit_list_insert(next, &walk->iterator_reverse) == NULL)
+				return -1;
 
 		if (error != GIT_EREVWALKOVER)
-			return git__rethrow(error, "Failed to prepare revision walk");
+			return -1;
 
 		walk->get_next = &revwalk_next_reverse;
 	}
 
 	walk->walking = 1;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 
@@ -550,12 +751,10 @@ static int prepare_walk(git_revwalk *walk)
 
 int git_revwalk_new(git_revwalk **revwalk_out, git_repository *repo)
 {
-	int error;
 	git_revwalk *walk;
 
 	walk = git__malloc(sizeof(git_revwalk));
-	if (walk == NULL)
-		return GIT_ENOMEM;
+	GITERR_CHECK_ALLOC(walk);
 
 	memset(walk, 0x0, sizeof(git_revwalk));
 
@@ -565,11 +764,12 @@ int git_revwalk_new(git_revwalk **revwalk_out, git_repository *repo)
 
 	if (walk->commits == NULL) {
 		git__free(walk);
-		return GIT_ENOMEM;
+		return -1;
 	}
 
 	git_pqueue_init(&walk->iterator_time, 8, commit_time_cmp);
 	git_vector_init(&walk->memory_alloc, 8, NULL);
+	git_vector_init(&walk->twos, 4, NULL);
 	alloc_chunk(walk);
 
 	walk->get_next = &revwalk_next_unsorted;
@@ -577,14 +777,13 @@ int git_revwalk_new(git_revwalk **revwalk_out, git_repository *repo)
 
 	walk->repo = repo;
 
-	error = git_repository_odb(&walk->odb, repo);
-	if (error < GIT_SUCCESS) {
+	if (git_repository_odb(&walk->odb, repo) < 0) {
 		git_revwalk_free(walk);
-		return error;
+		return -1;
 	}
 
 	*revwalk_out = walk;
-	return GIT_SUCCESS;
+	return 0;
 }
 
 void git_revwalk_free(git_revwalk *walk)
@@ -613,6 +812,7 @@ void git_revwalk_free(git_revwalk *walk)
 		git__free(git_vector_get(&walk->memory_alloc, i));
 
 	git_vector_free(&walk->memory_alloc);
+	git_vector_free(&walk->twos);
 	git__free(walk);
 }
 
@@ -648,8 +848,8 @@ int git_revwalk_next(git_oid *oid, git_revwalk *walk)
 	assert(walk && oid);
 
 	if (!walk->walking) {
-		if ((error = prepare_walk(walk)) < GIT_SUCCESS)
-			return git__rethrow(error, "Failed to load next revision");
+		if ((error = prepare_walk(walk)) < 0)
+			return -1;
 	}
 
 	error = walk->get_next(&next, walk);
@@ -659,11 +859,11 @@ int git_revwalk_next(git_oid *oid, git_revwalk *walk)
 		return GIT_EREVWALKOVER;
 	}
 
-	if (error < GIT_SUCCESS)
-		return git__rethrow(error, "Failed to load next revision");
+	if (error < 0)
+		return -1;
 
 	git_oid_cpy(oid, &next->oid);
-	return GIT_SUCCESS;
+	return 0;
 }
 
 void git_revwalk_reset(git_revwalk *walk)
diff --git a/tests-clar/revwalk/basic.c b/tests-clar/revwalk/basic.c
index cc88ec6..7d54ce9 100644
--- a/tests-clar/revwalk/basic.c
+++ b/tests-clar/revwalk/basic.c
@@ -148,14 +148,13 @@ void test_revwalk_basic__push_head(void)
 	cl_assert(i == 7);
 }
 
-void test_revwalk_basic__push_head_hide_glob(void)
+void test_revwalk_basic__push_head_hide_ref(void)
 {
 	int i = 0;
 	git_oid oid;
 
 	cl_git_pass(git_revwalk_push_head(_walk));
-	/* This is a hack, as we know this will only match the packed-test branch */
-	cl_git_pass(git_revwalk_hide_glob(_walk, "heads/packed-test*"));
+	cl_git_pass(git_revwalk_hide_ref(_walk, "refs/heads/packed-test"));
 
 	while (git_revwalk_next(&oid, _walk) == GIT_SUCCESS) {
 		i++;
@@ -164,3 +163,19 @@ void test_revwalk_basic__push_head_hide_glob(void)
 	/* git log HEAD --oneline --not refs/heads/packed-test | wc -l => 4 */
 	cl_assert(i == 4);
 }
+
+void test_revwalk_basic__push_head_hide_ref_nobase(void)
+{
+	int i = 0;
+	git_oid oid;
+
+	cl_git_pass(git_revwalk_push_head(_walk));
+	cl_git_pass(git_revwalk_hide_ref(_walk, "refs/heads/packed"));
+
+	while (git_revwalk_next(&oid, _walk) == GIT_SUCCESS) {
+		i++;
+	}
+
+	/* git log HEAD --oneline --not refs/heads/packed | wc -l => 7 */
+	cl_assert(i == 7);
+}
diff --git a/tests-clar/revwalk/mergebase.c b/tests-clar/revwalk/mergebase.c
new file mode 100644
index 0000000..91bc6ae
--- /dev/null
+++ b/tests-clar/revwalk/mergebase.c
@@ -0,0 +1,37 @@
+#include "clar_libgit2.h"
+
+static git_repository *_repo;
+
+void test_revwalk_mergebase__initialize(void)
+{
+	cl_git_pass(git_repository_open(&_repo, cl_fixture("testrepo.git")));
+}
+
+void test_revwalk_mergebase__cleanup(void)
+{
+	git_repository_free(_repo);
+}
+
+void test_revwalk_mergebase__single1(void)
+{
+	git_oid result, one, two, expected;
+
+	git_oid_fromstr(&one, "c47800c7266a2be04c571c04d5a6614691ea99bd ");
+	git_oid_fromstr(&two, "9fd738e8f7967c078dceed8190330fc8648ee56a");
+	git_oid_fromstr(&expected, "5b5b025afb0b4c913b4c338a42934a3863bf3644");
+
+	cl_git_pass(git_merge_base(&result, _repo, &one, &two));
+	cl_assert(git_oid_cmp(&result, &expected) == 0);
+}
+
+void test_revwalk_mergebase__single2(void)
+{
+	git_oid result, one, two, expected;
+
+	git_oid_fromstr(&one, "763d71aadf09a7951596c9746c024e7eece7c7af");
+	git_oid_fromstr(&two, "a65fedf39aefe402d3bb6e24df4d4f5fe4547750");
+	git_oid_fromstr(&expected, "c47800c7266a2be04c571c04d5a6614691ea99bd");
+
+	cl_git_pass(git_merge_base(&result, _repo, &one, &two));
+	cl_assert(git_oid_cmp(&result, &expected) == 0);
+}