1 files changed, 40 insertions, 0 deletions
diff --git a/src/cmd/dist/exec.go b/src/cmd/dist/exec.go
new file mode 100644
index 0000000..602b812
--- /dev/null
+++ b/src/cmd/dist/exec.go
@@ -0,0 +1,40 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"os/exec"
+	"strings"
+)
+
+// setDir sets cmd.Dir to dir, and also adds PWD=dir to cmd's environment.
+func setDir(cmd *exec.Cmd, dir string) {
+	cmd.Dir = dir
+	if cmd.Env != nil {
+		// os/exec won't set PWD automatically.
+		setEnv(cmd, "PWD", dir)
+	}
+}
+
+// setEnv sets cmd.Env so that key = value.
+func setEnv(cmd *exec.Cmd, key, value string) {
+	cmd.Env = append(cmd.Environ(), key+"="+value)
+}
+
+// unsetEnv sets cmd.Env so that key is not present in the environment.
+func unsetEnv(cmd *exec.Cmd, key string) {
+	cmd.Env = cmd.Environ()
+
+	prefix := key + "="
+	newEnv := []string{}
+	for _, entry := range cmd.Env {
+		if strings.HasPrefix(entry, prefix) {
+			continue
+		}
+		newEnv = append(newEnv, entry)
+		// key may appear multiple times, so keep going.
+	}
+	cmd.Env = newEnv
+}