This reverts commit 9a1983982a3e0ac012231e34d5688cfd76b2aaa5.

--- a/Cargo.toml
+++ b/Cargo.toml
@@ -32,11 +32,11 @@ version = "~1.0"
 version = "~2.33"
 
 [dependencies.git2]
-version = "~0.13"
+version = ">= 0.9"
 default-features = false
 
 [dependencies.memchr]
-version = "~2.3"
+version = ">= 2.2"
 
 [dependencies.slog]
 version = "~2.5"
diff --git a/src/stack.rs b/src/stack.rs
index ff7015c..d7cf3c8 100644
--- a/src/stack.rs
+++ b/src/stack.rs
@@ -29,9 +29,9 @@ pub fn working_stack<'repo>(
     }
 
     let mut revwalk = repo.revwalk()?;
-    revwalk.set_sorting(git2::Sort::TOPOLOGICAL)?;
+    revwalk.set_sorting(git2::Sort::TOPOLOGICAL);
     revwalk.push_head()?;
-    revwalk.simplify_first_parent()?;
+    revwalk.simplify_first_parent();
     debug!(logger, "head pushed"; "head" => head.name());
 
     let base_commit = match user_provided_base {