Re: Bug report: checkout-index --temp path is not always relative to the current directory

> In the section on using --temp, 'git help checkout-index' says:
>
> "The path field is always relative to the current directory and the
> temporary file names are always relative to the top level directory."
>
> However, this can be false when an absolute path to the file is provided.

> Reproduction:
>
> ~$ git version
> git version 2.2.1
> ~$ mkdir demo
> ~$ cd demo
> ~/demo$ mkdir a
> ~/demo$ echo "a" > a/f
> ~/demo$ mkdir b
> ~/demo$ echo "b" > b/f
> ~/demo$ git init .
> Initialized empty Git repository in ~/demo/.git/
> ~/demo$ git add .
> ~/demo$ git commit -m "init"
> [master (root-commit) 2afa910] init
>  2 files changed, 2 insertions(+)
>  create mode 100644 a/f
>  create mode 100644 b/f
> ~/demo$ echo "b2" > b/f
> ~/demo$ cd a
> ~/demo/a$ git checkout-index --temp -- `git rev-parse --show-toplevel`/b/f
> .merge_file_xm8RTd f
> ~/demo/a$ cat ../.merge_file_xm8RTd
> b
>
> Note that if f in the checkout-index output is interpreted as relative
> to the current directory, it would refer to a/f, whereas in fact is it
> b/f.
>
> This led to https://github.com/golang/go/issues/9476.
>
> Thanks,
> Josh