Add `BROWSER` support to `OpenURL()`

If the `BROWSER` environment variable is set, open the given URL using
the command specified in the variable.

Run the command in a shell process, either from the `SHELL` environment
variable or `/bin/sh` on Unix OSes. Run it through `cmd` on Windows.

Essentially repurposes my code from
https://github.com/pkg/browser/pull/14.

1 files changed, 29 insertions, 0 deletions

diff --git a/browserenv_unix_test.go b/browserenv_unix_test.go
new file mode 100644
index 0000000..bcc7c2d
--- /dev/null
+++ b/browserenv_unix_test.go
@@ -0,0 +1,29 @@
+// +build !windows
+
+package browserenv
+
+import (
+	"fmt"
+	"os"
+	"reflect"
+	"testing"
+)
+
+func TestBrowserCommand(t *testing.T) {
+	envValue := "open -a Firefox"
+	url := "https://duckduckgo.com"
+
+	cmd := browserCommand(envValue, url)
+
+	shell := os.Getenv("SHELL")
+	if shell == "" {
+		shell = "/bin/sh"
+	}
+
+	browserCommand := fmt.Sprintf("%s '%s'", envValue, url)
+
+	wantArgs := []string{shell, "-c", browserCommand}
+	if !reflect.DeepEqual(cmd.Args, wantArgs) {
+		t.Errorf("got args '%#v' want '%#v'", cmd.Args, wantArgs)
+	}
+}