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, 15 insertions, 0 deletions

diff --git a/browserenv_windows.go b/browserenv_windows.go
new file mode 100644
index 0000000..ef9c2b7
--- /dev/null
+++ b/browserenv_windows.go
@@ -0,0 +1,15 @@
+package browserenv
+
+import "fmt"
+
+var shellArgs = []string{"cmd", "/c"}
+
+// TODO
+func shell() (args []string) {
+	return shellArgs
+}
+
+// TODO
+func fmtBrowserCommand(browser, url string) string {
+	return fmt.Sprintf("%s %s", browser, url)
+}