build: lookup the right git binary on WSL

Signed-off-by: CrazyMax <crazy-max@users.noreply.github.com>

util/gitutil/gitpath_unix.go

@@ -0,0 +1,42 @@
+//go:build !windows
+// +build !windows
+
+package gitutil
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/moby/sys/mountinfo"
+)
+
+func gitPath(wd string) (string, error) {
+	// On WSL2 we need to check if the current working directory is mounted on
+	// a Windows drive and if so, we need to use the Windows git executable.
+	if os.Getenv("WSL_DISTRO_NAME") != "" && wd != "" {
+		// ensure any symlinks are resolved
+		wdPath, err := filepath.EvalSymlinks(wd)
+		if err != nil {
+			return "", err
+		}
+		mi, err := mountinfo.GetMounts(mountinfo.ParentsFilter(wdPath))
+		if err != nil {
+			return "", err
+		}
+		// find the longest mount point
+		var idx, maxlen int
+		for i := range mi {
+			if len(mi[i].Mountpoint) > maxlen {
+				maxlen = len(mi[i].Mountpoint)
+				idx = i
+			}
+		}
+		if mi[idx].FSType == "9p" {
+			if p, err := exec.LookPath("git.exe"); err == nil {
+				return p, nil
+			}
+		}
+	}
+	return exec.LookPath("git")
+}