thodg/libgit2

diff --git a/src/commit.c b/src/commit.c
index 8844825..fa33b52 100644
--- a/src/commit.c
+++ b/src/commit.c
@@ -51,41 +51,71 @@ void git_commit_mark_uninteresting(git_commit *commit)
 	}
 }
 
-git_commit *git_commit_lookup(git_revpool *pool, const git_oid *id)
+git_commit *git_commit_parse(git_revpool *pool, const git_oid *id)
 {
-    git_obj commit_obj;
     git_commit *commit = NULL;
 
-    if (pool == NULL || pool->db == NULL)
+    if ((commit = git_commit_lookup(pool, id)) == NULL)
         return NULL;
 
-    /*
-     * TODO: check if the commit is already cached in the
-     * revpool instead of loading it from the odb
-     */
+    if (git_commit_parse_existing(commit) < 0)
+        goto error_cleanup;
 
-    if (git_odb_read(&commit_obj, pool->db, id) < 0)
-        return NULL;
+    return commit;
+
+error_cleanup:
+    free(commit);
+    return NULL;
+}
+
+int git_commit_parse_existing(git_commit *commit)
+{
+    git_obj commit_obj;
+
+    if (commit->parsed)
+        return 0;
+
+    if (commit->pool == NULL || commit->pool->db == NULL)
+        return -1;
+
+    if (git_odb_read(&commit_obj, commit->pool->db, &commit->id) < 0)
+        return -1;
 
     if (commit_obj.type != GIT_OBJ_COMMIT)
         goto error_cleanup;
 
+    if (git_commit__parse_buffer(commit, commit_obj.data, commit_obj.len) < 0)
+        goto error_cleanup;
+
+    git_obj_close(&commit_obj);
+
+    return 0;
+
+error_cleanup:
+    git_obj_close(&commit_obj);
+    return -1;
+}
+
+git_commit *git_commit_lookup(git_revpool *pool, const git_oid *id)
+{
+    git_commit *commit = NULL;
+
+    if (pool == NULL || pool->db == NULL)
+        return NULL;
+
     commit = git__malloc(sizeof(git_commit));
+
+    if (commit == NULL)
+        return NULL;
+
     memset(commit, 0x0, sizeof(git_commit));
 
     git_oid_cpy(&commit->id, id);
     commit->pool = pool;
 
-    if (git_commit__parse_buffer(commit, commit_obj.data, commit_obj.len) < 0)
-        goto error_cleanup;
+    git_commit_list_insert(&pool->commits, commit);
 
     return commit;
-
-error_cleanup:
-    git_obj_close(&commit_obj);
-    free(commit);
-
-    return NULL;
 }
 
 int git_commit__parse_time(time_t *commit_time, char *buffer, const char *buffer_end)
@@ -111,8 +141,8 @@ int git_commit__parse_time(time_t *commit_time, char *buffer, const char *buffer
 
 int git_commit__parse_oid(git_oid *oid, char **buffer_out, const char *buffer_end, const char *header)
 {
-    size_t sha_len = GIT_OID_HEXSZ;
-    size_t header_len = strlen(header);
+    const size_t sha_len = GIT_OID_HEXSZ;
+    const size_t header_len = strlen(header);
 
     char *buffer = *buffer_out;
 
diff --git a/src/commit.h b/src/commit.h
index 7ab2d54..3a6b706 100644
--- a/src/commit.h
+++ b/src/commit.h
@@ -30,6 +30,8 @@ int git_commit__parse_oid(git_oid *oid, char **buffer_out, const char *buffer_en
 int git_commit__parse_buffer(git_commit *commit, void *data, size_t len);
 int git_commit__parse_time(time_t *commit_time, char *buffer, const char *buffer_end);
 
+int git_commit_parse_existing(git_commit *commit);
+
 void git_commit_list_insert(git_commit_list **list, git_commit *commit);
 
 #endif
diff --git a/src/git/commit.h b/src/git/commit.h
index ea59a21..1a57ba7 100644
--- a/src/git/commit.h
+++ b/src/git/commit.h
@@ -17,7 +17,17 @@ GIT_BEGIN_DECL
 typedef struct git_commit git_commit;
 
 /**
- * Lookup a commit from a revision pool, and parse it if needed.
+ * Locate a reference to a commit without loading it.
+ * @param pool the pool to use when locating the commit.
+ * @param id identity of the commit to locate.  If the object is
+ *        an annotated tag it will be peeled back to the commit.
+ * @return the commit; NULL if the commit could not be created
+ */
+GIT_EXTERN(git_commit *) git_commit_lookup(git_revpool *pool, const git_oid *id);
+
+/**
+ * Locate a reference to a commit, and try to load and parse it it from
+ * the commit cache or the object database.
  * @param pool the pool to use when parsing/caching the commit.
  * @param id identity of the commit to locate.  If the object is
  *        an annotated tag it will be peeled back to the commit.
@@ -25,7 +35,7 @@ typedef struct git_commit git_commit;
  *         pool's git_odb, or if the commit is present but is
  *         too malformed to be parsed successfully.
  */
-GIT_EXTERN(git_commit *) git_commit_lookup(git_revpool *pool, const git_oid *id);
+GIT_EXTERN(git_commit *) git_commit_parse(git_revpool *pool, const git_oid *id);
 
 /**
  * Get the id of a commit.
diff --git a/src/revwalk.c b/src/revwalk.c
index 96f3444..fe6f9f2 100644
--- a/src/revwalk.c
+++ b/src/revwalk.c
@@ -41,31 +41,42 @@ git_revpool *gitrp_alloc(git_odb *db)
 
 void gitrp_free(git_revpool *walk)
 {
+    git_commit_list *list;
+
+    list = walk->commits;
+    while (list)
+    {
+        free(list->commit);
+        list = list->next;
+    }
+
 	free(walk);
 }
 
 void gitrp_push(git_revpool *pool, git_commit *commit)
 {
+    if (commit->pool != pool)
+        return;
+
     if ((commit->flags & GIT_COMMIT_SEEN) != 0)
         return;
 
-    /* FIXME:
-     * Unparsed commit objects? Where do these come from?
-     * Do we need to handle them?
-     */
     if (!commit->parsed)
-        return;
+    {
+        if (git_commit_parse_existing(commit) < 0)
+            return;
+    }
 
     commit->flags |= GIT_COMMIT_SEEN;
 
-    git_commit_list_insert(&pool->commits, commit);
+    git_commit_list_insert(&pool->roots, commit);
 }
 
 void gitrp_prepare_walk(git_revpool *pool)
 {
     // TODO: sort commit list based on walk ordering
 
-    pool->iterator = pool->commits;
+    pool->iterator = pool->roots;
     pool->walking = 1;
 }
 
diff --git a/src/revwalk.h b/src/revwalk.h
index edf57b4..34ff337 100644
--- a/src/revwalk.h
+++ b/src/revwalk.h
@@ -8,6 +8,7 @@ struct git_revpool {
 	git_odb *db;
     git_commit_list *iterator;
     git_commit_list *commits;
+    git_commit_list *roots;
 
     unsigned walking:1,
              topological_sort:1;