Paths on Windows should be compared case-insensitive

[kjk]

PS C:\Users\kjk\src\go\src\github.com\kjk\kjktools.org> gci Env:\GOPATH

Name                           Value
----                           -----
GOPATH                         c:\Users\kjk\src\go

PS C:\Users\kjk\src\go\src\github.com\kjk\kjktools.org> dep ensure
project not in a GOPATH

Notice that the project is in GOPATH except GOPATH is c:\... and filesystem path is C:\....

I fixed it by changing GOPATH to match fs name, but:

• this might happen to other people who might have less luck figuring this out
• I assume there might be other scenarios where it breaks

OSX is also case-insensitive by default although might be formatted with case-sensitive version of hfs.

[sdboyer]

Thanks for the issue report!

We've actually spent quite a bit of time on this, and have some pretty sophisticated logic in place - see #296 and #395. We must have a regression somewhere, and one not caught by our tests. (Or we never got it right in the first place)

We can't actually go by OS here, as case sensitivity - as you note - is not an OS property, but a filesystem one.

If you could do a bit of poking and see which part of HasFilepathPrefix() is getting it wrong here, that'd be very helpful. If that's not where the problem is, then we stopped using it in the right place somewhere along the line, and that should be an easier fix (though really needs a regression test)

[kjk]

I'm pretty sure that the issue is: https://github.com/golang/dep/blob/master/internal/fs/fs.go#L32 i.e. filepath.VolumeName() is case-sensitive, so it should be sth. like:

	if strings.ToLower(filepath.VolumeName(path)) != strings.ToLower(filepath.VolumeName(prefix)) {
		return false
	}

Not actually tested.

[sdboyer]

seems like a good first PR to me - that fix, plus some tests to enforce it 😄

[mikijov]

@kjk, I am looking for a simple bug to get my feet wet. If you don't mind, I will prepare a PR for this.

[kjk]

@mikijov go for it

[mikijov]

PR is in. Not sure if I should ask someone to review or if they will pick it up automatically.