gutter colors not showing change on correct line about vim-gitgutter

[airblade]

I agree that it doesn't show what you would expect. It's a consequence of the way git-diff works.

If you diff your file on the command line, you'll get something like this:

$ git diff -U0
diff --git i/path/to/file.go w/path/to/file.go
index <sha>..<sha> 100644
--- i/path/to/file.go
+++ i/path/to/file.go
@@ -5 -5,4 @@ func main()
- c := a + b
+ string1 := "hddi"
+ string2 := "bye"
+ fmt.Printf("%d, %d", string1, string2)
+ c := a + b+ 4

The hunk header (@@ -5 -5+4 @@) says that 1 line was removed and 4 lines were added. We can infer that 1 line was changed and 3 were added, but not which line was which.

When a hunk contains modifications and additions, gitgutter assumes that the modifications come first – there's nothing else it can do.