Remove Windows support

Unfortunately, I don't have the expertise or bandwidth to maintain
the Windows support in Litestream. I'm open to re-adding support in
the future but right now it is hindering development and is not
well-tested or well-used.

internal/internal.go

@@ -132,7 +132,7 @@ func MkdirAll(path string, mode os.FileMode, uid, gid int) error {
 
 	if j > 1 {
 		// Create parent.
-		err = MkdirAll(fixRootDirectory(path[:j-1]), mode, uid, gid)
+		err = MkdirAll(path[:j-1], mode, uid, gid)
 		if err != nil {
 			return err
 		}
@@ -154,6 +154,15 @@ func MkdirAll(path string, mode os.FileMode, uid, gid int) error {
 	return nil
 }
 
+// Fileinfo returns syscall fields from a FileInfo object.
+func Fileinfo(fi os.FileInfo) (uid, gid int) {
+	if fi == nil {
+		return -1, -1
+	}
+	stat := fi.Sys().(*syscall.Stat_t)
+	return int(stat.Uid), int(stat.Gid)
+}
+
 // ParseSnapshotPath parses the index from a snapshot filename. Used by path-based replicas.
 func ParseSnapshotPath(s string) (index int, err error) {
 	a := snapshotPathRegex.FindStringSubmatch(s)

internal/internal_unix.go

@@ -1,21 +0,0 @@
-// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
-
-package internal
-
-import (
-	"os"
-	"syscall"
-)
-
-// Fileinfo returns syscall fields from a FileInfo object.
-func Fileinfo(fi os.FileInfo) (uid, gid int) {
-	if fi == nil {
-		return -1, -1
-	}
-	stat := fi.Sys().(*syscall.Stat_t)
-	return int(stat.Uid), int(stat.Gid)
-}
-
-func fixRootDirectory(p string) string {
-	return p
-}

internal/internal_windows.go

@@ -1,22 +0,0 @@
-// +build windows
-
-package internal
-
-import (
-	"os"
-)
-
-// Fileinfo returns syscall fields from a FileInfo object.
-func Fileinfo(fi os.FileInfo) (uid, gid int) {
-	return -1, -1
-}
-
-// fixRootDirectory is copied from the standard library for use with mkdirAll()
-func fixRootDirectory(p string) string {
-	if len(p) == len(`\\?\c:`) {
-		if os.IsPathSeparator(p[0]) && os.IsPathSeparator(p[1]) && p[2] == '?' && os.IsPathSeparator(p[3]) && p[5] == ':' {
-			return p + `\`
-		}
-	}
-	return p
-}