Fix a regression introduced by #6008 adding bind mounts without desti…

…nation two times

e2e/actions/actions.go

@@ -2270,6 +2270,7 @@ func E2ETests(env e2e.TestEnv) testhelper.Tests {
 		"issue 5599":            c.issue5599,           // https://github.com/hpcng/singularity/issues/5599
 		"issue 5631":            c.issue5631,           // https://github.com/hpcng/singularity/issues/5631
 		"issue 5690":            c.issue5690,           // https://github.com/hpcng/singularity/issues/5690
+		"issue 6165":            c.issue6165,           // https://github.com/hpcng/singularity/issues/6165
 		"network":               c.actionNetwork,       // test basic networking
 		"binds":                 c.actionBinds,         // test various binds
 		"exit and signals":      c.exitSignals,         // test exit and signals propagation

e2e/actions/regressions.go

@@ -684,3 +684,36 @@ func (c actionTests) invalidRemote(t *testing.T) {
 	)
 
 }
+
+// Check that a bind mount without a destination is not added two times.
+func (c actionTests) issue6165(t *testing.T) {
+	e2e.EnsureImage(t, c.env)
+
+	workspace, cleanup := e2e.MakeTempDir(t, c.env.TestDir, "issue6165-", "")
+	defer e2e.Privileged(cleanup)
+
+	hostCanaryFile := filepath.Join(workspace, "file")
+
+	if err := fs.Touch(hostCanaryFile); err != nil {
+		t.Fatalf("failed to create canary_file: %s", err)
+	}
+
+	c.env.RunSingularity(
+		t,
+		e2e.WithProfile(e2e.UserProfile),
+		e2e.WithCommand("exec"),
+		e2e.WithArgs(
+			"--contain",
+			"--bind", hostCanaryFile,
+			c.env.ImagePath,
+			"test", "-f", hostCanaryFile,
+		),
+		e2e.ExpectExit(
+			0,
+			e2e.ExpectError(
+				e2e.UnwantedContainMatch,
+				"destination is already in the mount point list",
+			),
+		),
+	)
+}

pkg/runtime/engine/singularity/config/config.go

@@ -408,6 +408,8 @@ func ParseBindPath(paths []string) ([]BindPath, error) {
 				}
 				binds = append(binds, bp)
 				elem = 0
+				bind = ""
+				continue
 			}
 			// new bind path
 			bind = s