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, 25 insertions, 0 deletions

diff --git a/browserenv_unix.go b/browserenv_unix.go
new file mode 100644
index 0000000..e6416f8
--- /dev/null
+++ b/browserenv_unix.go
@@ -0,0 +1,25 @@
+// +build !windows
+
+package browserenv
+
+import (
+	"fmt"
+	"os"
+)
+
+// TODO
+func shell() (args []string) {
+	shell := os.Getenv("SHELL")
+
+	if shell == "" {
+		shell = "/bin/sh"
+	}
+
+	return []string{shell, "-c"}
+}
+
+// TODO
+func fmtBrowserCommand(browser, url string) string {
+	// TODO: handle %s in browser command
+	return fmt.Sprintf("%s '%s'", browser, url)
+}