plumbing.Reference.IsBranch is not working well on windows

[mpppk]

To Reproduce the problem

1. Create some branches

> git branch
master
some_features

2. Execute below code.

r, _ := git.PlainOpen(".")
refs, _ := r.References()
refs.ForEach(func(ref *plumbing.Reference) error {
	fmt.Println(ref.Name(), ref.IsBranch())
	return nil
})

Expected behavior

refs\heads\some_features true
refs\heads\master true
refs\remotes\origin\HEAD false
refs\remotes\origin\some_features false
refs\remotes\origin\master false
HEAD false

IsBranch() should return true if reference name is "master" or "some_features".

Actual behavior

refs/remotes/origin/master false
refs\heads\some_features false
refs\heads\master false
refs\remotes\origin\HEAD false
refs\remotes\origin\some_features false
refs\remotes\origin\master false
HEAD false

There are two problems.

1. Path separators "/" and "\" are mixed
2. refs\heads\master and refs\heads\some_features are branch but IsBranch() return false

Cause of problems

Cause of the path separators are mixed

If reference is retrieved from refs/heads, refs/remotes and refs/tags, path separator is determined by DotGit.fs.Join when read reference path.
So path separator will be "\" on windows.

dotgit.go 468

func (d *DotGit) readReferenceFile(refsPath, refFile string) (ref *plumbing.Reference, err error) {
	path := d.fs.Join(refsPath, refFile)

But if reference is retrieved from packed-refs, the path written in the file has "/" as path separator even if it on windows and the path is used as reference path direct.

packed-refs example:

# pack-refs with: peeled fully-peeled
65fdeb52c589aed517facc3b2b0edefe5d26518d refs/remotes/origin/master
^29c35f9a455bf5ed601ec47d3ca93da079ce428a

Cause why IsBranch() return false even if it is branch

Windows path separator will be "\" but IsBranch() expect "/"

func (r *Reference) IsBranch() bool {
	return strings.HasPrefix(string(r.n), refHeadPrefix)
}

const (
	refPrefix       = "refs/"
	refHeadPrefix   = refPrefix + "heads/"
	refTagPrefix    = refPrefix + "tags/"
	refRemotePrefix = refPrefix + "remotes/"
	refNotePrefix   = refPrefix + "notes/"
	symrefPrefix    = "ref: "
)

Possible Fix

I think there are two ways to fix these problems.

1. Always join reference path by "/"
2. Use strings.Join when concat RefsPrefixes and replace "/" to "\" when retrieve reference path from packed-refs if running on windows.

[mcuadros]

@mpppk can you check if still happens in the current master?

[mcuadros]

Closed, due to inactivity.