Diff detected on correctly formatted file

[mhofstetter]

What version of GCI are you using?

v0.8.4

Reproduce Steps

Running gci diff on a properly formatted source code file results in a diff. Same applies for the command write.

It seems as the problem is an unintended modification of the underlying src byte array when modifying head & tail which are slices based on the same array.

-> https://github.com/daixiang0/gci/blob/master/pkg/gci/gci.go#L159-L160

./dist/gci diff <...>/github.com/daixiang0/gci/pkg/gci/internal/testdata/with-comment-and-alias.out.go --section Standard --section Default --section "Prefix(github.com/daixiang0)"    
--- /<...>/github.com/daixiang0/gci/pkg/gci/internal/testdata/with-comment-and-alias.out.go
+++ /<...>/github.com/daixiang0/gci/pkg/gci/internal/testdata/with-comment-and-alias.out.go
@@ -1,8 +1,8 @@
 package main
 
+import (
+	"fmt"
 
-import (	"fmt"
-
 	_ "github.com/golang" // golang
 
 	"github.com/daixiang0/gci"

What did you expect to see?

Properly formatted files should not print any diff.

What did you see instead?

Diff gets printed due to uncorrect view of source file.