clipdel: Support getting pattern from standard input

[ferki]

I'm using clipmenu together with pass (and passmenu :)), and
wanted to make sure that pass would remove passwords both from the
clipboard and the clipboard history.

I had to slightly patch pass for that locally, where I also figured it
would be best to simply pipe the password string into clipdel, instead
of passing it as an argument.

This patch makes clipdel look for a pattern coming from standard input
if there's no pattern passed as an argument.

Please review, and let me know if you need me to improve it, or to open
an issue instead for further discussions.

[cdown]

Thanks! Conceptually this looks fine, just a couple of things:

1. User experience is not great if invoked incorrectly now (ie. you don't get the "no pattern provided, see --help" message). This can be mitigated by checking if connected to a terminal with [[ -t 1 ]].
2. Ideally use shell builtins where available (it's likely not harmful in this case, but they have fewer shenanigans than when using $(). You can use read -r with no IFS set for this.

[ferki]

Thanks for your patience here!

I'd like to update this PR, and most of the steps are clear to me (rebase on top of current master, and replace cat usage with IFS= read -r).

I think I need some clarifications on the feedback about checking for a connected terminal, though:

1. User experience is not great if invoked incorrectly now (ie. you don't get the "no pattern provided, see --help" message). This can be mitigated by checking if connected to a terminal with [[ -t 1 ]].

Where should this [[ -t 1 ]] check go? Into the if that decides about printing the error message, or into a new if that decides how to obtain a value for raw_pattern? Perhaps both, or even somewhere else?

[cdown]

Sorry this went stale -- this is still okay, though. Probably the terminal check can just be around raw_pattern assignment itself.

[ferki]

No worries, thanks for the feedback!

I've rebased my changes on top of current master, and made a more explicit check for the various sources of possible input. Let me know how it fits the codebase now!

[cdown]

Thanks! Looks good to me.