Implement a more robust algorithm for opening web links on unices

[bouncepaw]

Changes

• webbrowser.Open now tries to use $BROWSER env variable before giving up if there is no xdg-open installed.
• Do not check for Xorg program anymore. I think it is safe to expect that there is X installed if $DISPLAY is set.
• Add some comments.

TTY browsers

As a comment in this PR mentions, I couldn't implement it. Something goes wrong when trying to restore amfora after closing a terminal browser (running in foreground, of course). If anyone wishes to implement it, they could check this:

• termenv's screen.go for altscreen sequences
• this SO answer for information on how to launch ncurses programs

[makew0rld]

Thanks for adding this! I'm not sure how many people use $BROWSER but there's no harm in supporting it. As for TTY browsers, I'm okay with leaving that for now.

Please see my comments below.

[makew0rld]

Suggested change

	case xdgOpenNotFoundErr == nil || envBrowser != "":
	case envBrowser != "":
	// Prefer $BROWSER over xdg-open
	// Use start rather than run or output in order
	// to make browser running in background.
	if err := exec.Command(envBrowser, url).Start(); err != nil {
	return "", err
	}
	return "Opened in $BROWSER", nil
	case xdgOpenNotFoundErr == nil:

Your code does not seem to make use of the $BROWSER variable at all, I assume that's a mistake. My suggestion above makes use of the var if it's available, and use xdg-open otherwise.

[bouncepaw]

Yeah, that's a mistake. There were two similar case-blocks and I smashed them together without second thought. Gotta fix this.

I think xdg-open should be used first because it's more idiomatic (I think) and is also similar to how this function is implemented for other platforms.

[makew0rld]

I thought $BROWSER should be first because it's something the user manually sets, so it's more likely to be a custom specific choice than xdg-open. Plus it's only used by CLI software, so a user could use it to differentiate between links in CLI and GUI.

[bouncepaw]

That's a good point (you've almost convinced me), but consider xdg-open's source code. It seems to me that xdg-open depends on the $BROWSER variable in some cases. Therefore, xdg-open is more universal and should be used first.

[makew0rld]

Oh, I had no idea! Ok, I agree. I will merge this soon, consider it complete.