--env-file: simple line-delimited

match dock functionality, and not try to achieve shell-sourcing compatibility

Docker-DCO-1.1-Signed-off-by: Vincent Batts <vbatts@redhat.com> (github: vbatts)

opts/envfile.go

@@ -0,0 +1,35 @@
+package opts
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strings"
+)
+
+/*
+Read in a line delimited file with environment variables enumerated
+*/
+func ParseEnvFile(filename string) ([]string, error) {
+	fh, err := os.Open(filename)
+	if err != nil {
+		return []string{}, err
+	}
+	defer fh.Close()
+
+	lines := []string{}
+	scanner := bufio.NewScanner(fh)
+	for scanner.Scan() {
+		line := scanner.Text()
+		// line is not empty, and not starting with '#'
+		if len(line) > 0 && !strings.HasPrefix(line, "#") {
+			if strings.Contains(line, "=") {
+				data := strings.SplitN(line, "=", 2)
+				lines = append(lines, fmt.Sprintf("%s=%s", data[0], data[1]))
+			} else {
+				lines = append(lines, fmt.Sprintf("%s=%s", line, os.Getenv(line)))
+			}
+		}
+	}
+	return lines, nil
+}