Fix the ranges in unified diff output

CHANGELOG.md

@@ -15,6 +15,7 @@ All notable changes to similar are documented here.
 * Added a compacting step to clean up diffs.  This results in nicer looking diffs and
   fewer edits.  This is happening automatically for captured diffs and is exposed
   through the `Capture` type.
+* Fix incorrect ranges in unified diff output.
 
 ## 1.2.2
 

src/snapshots/similar__udiff__unified_diff.snap

@@ -4,7 +4,7 @@ expression: "&diff.unified_diff().header(\"a.txt\", \"b.txt\").to_string()"
 ---
 --- a.txt
 +++ b.txt
-@@ -15,3 +19,3 @@
+@@ -16,7 +16,7 @@
  p
  q
  r
@@ -13,7 +13,7 @@ expression: "&diff.unified_diff().header(\"a.txt\", \"b.txt\").to_string()"
  t
  u
  v
-@@ -37,3 +41,3 @@
+@@ -38,7 +38,7 @@
  L
  M
  N

src/snapshots/similar__udiff__unified_diff_newline_hint-2.snap

@@ -4,7 +4,7 @@ expression: "&diff.unified_diff().missing_newline_hint(false).header(\"a.txt\",\
 ---
 --- a.txt
 +++ b.txt
-@@ -0 +0 @@
+@@ -1 +1 @@
 -a
 +b
 

src/snapshots/similar__udiff__unified_diff_newline_hint.snap

@@ -4,7 +4,7 @@ expression: "&diff.unified_diff().header(\"a.txt\", \"b.txt\").to_string()"
 ---
 --- a.txt
 +++ b.txt
-@@ -0 +0 @@
+@@ -1 +1 @@
 -a
 +b
 \ No newline at end of file

src/text/snapshots/similar__text__unified_diff.snap

@@ -4,7 +4,7 @@ expression: "&diff.unified_diff().context_radius(3).header(\"old\", \"new\").to_
 ---
 --- old
 +++ new
-@@ -0 +2 @@
+@@ -1,3 +1,3 @@
  Hello World
 -some stuff here
 +some amazing stuff here

src/udiff.rs

@@ -24,7 +24,6 @@
 //! The former uses [`DiffableStr::to_string_lossy`], the latter uses
 //! [`DiffableStr::as_bytes`] for each line.
 #[cfg(feature = "text")]
-use std::ops::Range;
 use std::{fmt, io};
 
 use crate::iter::AllChangesIter;
@@ -46,10 +45,6 @@ impl fmt::Display for MissingNewlineHint {
 struct UnifiedDiffHunkRange(usize, usize);
 
 impl UnifiedDiffHunkRange {
-    fn new(range: Range<usize>) -> UnifiedDiffHunkRange {
-        UnifiedDiffHunkRange(range.start, range.end)
-    }
-
     fn start(&self) -> usize {
         self.0
     }
@@ -61,7 +56,7 @@ impl UnifiedDiffHunkRange {
 
 impl fmt::Display for UnifiedDiffHunkRange {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        let mut beginning = self.start();
+        let mut beginning = self.start() + 1;
         let len = self.end() - self.start();
         if len == 1 {
             write!(f, "{}", beginning)
@@ -84,9 +79,15 @@ pub struct UnifiedHunkHeader {
 impl UnifiedHunkHeader {
     /// Creates a hunk header from a (non empty) slice of diff ops.
     pub fn new(ops: &[DiffOp]) -> UnifiedHunkHeader {
+        let first = ops[0];
+        let last = ops[ops.len() - 1];
+        let old_start = first.old_range().start;
+        let new_start = first.new_range().start;
+        let old_end = last.old_range().end;
+        let new_end = last.new_range().end;
         UnifiedHunkHeader {
-            old_range: UnifiedDiffHunkRange::new(ops[0].old_range()),
-            new_range: UnifiedDiffHunkRange::new(ops[ops.len() - 1].new_range()),
+            old_range: UnifiedDiffHunkRange(old_start, old_end),
+            new_range: UnifiedDiffHunkRange(new_start, new_end),
         }
     }
 }