Try modifying diff hunk with 'unidiff'

Testing out 'unidiff' to build the patch. Trying to see if it will
adjust the line numbers automatically when the patch is modified.
Doesn't look like it. Seems like it has a nice interface, though.

Still having trouble applying the patch due to complaints of patch
format errors.

1 files changed, 52 insertions, 0 deletions

diff --git a/src/lib.rs b/src/lib.rs
index 6db5c67..5ac1a74 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -147,4 +147,56 @@ mod tests {
 "#,
         );
     }
+
+    #[test]
+    fn unified_diff() {
+        use unidiff::PatchSet;
+
+        let diff = r#"--- a/command/pr.go
++++ b/command/pr.go
+@@ -1,9 +1,11 @@
+ package command
+ 
+ import (
++	"bufio" // used to input comment
+ 	"errors"
+ 	"fmt"
+ 	"io"
++	"os" // used to input comment
+"#;
+
+        let mut patch = PatchSet::new();
+        patch.parse(diff).unwrap();
+
+        println!("{:?}", patch);
+        println!("{}", patch);
+
+        let lines = patch.files_mut()[0].hunks_mut()[0].lines_mut();
+
+        // for line in &lines {
+        //     if line.is_removed() {
+        //     } else if line.is_added() {
+        //         line.line_type = unidiff::LINE_TYPE_CONTEXT.to_owned();
+        //     }
+        // }
+
+        lines
+            .iter_mut()
+            .filter(|l| !l.is_removed())
+            // .map(|l| {
+            .for_each(|l| {
+                if l.is_added() {
+                    l.line_type = unidiff::LINE_TYPE_CONTEXT.to_owned();
+                }
+            });
+
+        lines[lines.len() - 2].line_type = unidiff::LINE_TYPE_REMOVED.to_owned();
+
+        patch.files_mut()[0].hunks_mut()[0].append(unidiff::Line::new(
+            r#"	"os""#,
+            unidiff::LINE_TYPE_ADDED,
+        ));
+
+        println!("{}", patch);
+    }
 }