fix: Use git apply --3way when pushing

Some patches can only be applied correctly with a 3-way merge. When pushing
patches, StGit already generates/uses diffs that have the appropriate id
hashes to use `git apply --3way`, so just need to use that option.

Fixes: #225

Author: jpgrayson

src/stupid/mod.rs

@@ -167,7 +167,7 @@ impl<'repo, 'index> StupidContext<'repo, 'index> {
 
         let apply_output = self
             .git_in_work_root()
-            .args(["apply", "--cached"]) // --3way
+            .args(["apply", "--cached", "--3way"])
             .stdin(diff_tree_child.stdout.take().unwrap())
             .stdout(Stdio::null())
             .output_git()?
@@ -212,7 +212,7 @@ impl<'repo, 'index> StupidContext<'repo, 'index> {
 
         let apply_output = self
             .git_in_work_root()
-            .args(["apply", "--cached"]) // --3way
+            .args(["apply", "--cached", "--3way"])
             .stdin(Stdio::piped())
             .stdout(Stdio::null())
             .in_and_out(&diff)?;