Fix diff text whitespace

Author: peter-evans

format.go

@@ -10,6 +10,9 @@ import (
 func DiffText(diffs []DiffLine) string {
 	s := make([]string, len(diffs))
 	for i, l := range diffs {
+		if len(l.Text) == 0 && l.Type == Equal {
+			continue
+		}
 		prefix := " "
 		switch l.Type {
 		case Insert:

patience_test.go

@@ -223,7 +223,7 @@ int main(int argc, char **argv)
 }`, "\n")
 
 	want := ` #include <stdio.h>
- 
+
 +int fib(int n)
 +{
 +    if(n > 2)
@@ -243,7 +243,7 @@ int main(int argc, char **argv)
          printf("%d\n", foo);
      }
  }
- 
+
 -int fact(int n)
 -{
 -    if(n > 1)