Alias support for subcommands

[mqudsi]

Suggestion for fish 3.0: support aliasing command subcommand to something

Reason: it'll let you do cool things with git (surprise!) like alias 'git log' 'git log --name-status' since there is not yet a git option for log.nameStatus or similar.

It would be very straightforward to simply check if arg == aliased arg and call the alternative command in its place or else shell out to the actual command.

[floam]

Be warned, the standard answer you will get here will be "use an abbr". But this could be useful in select situations and it wouldn't hurt anybody if alias did handle it. Probably if you just go ahead and implement a smarter alias that can create such a function there should be no good argument against merging it specifically. (YMMV).

[mqudsi]

Thanks @floam.

The way I view aliases with the same name as an existing command is that they should provide the same service in a compatible fashion, just with added niceties. I like to only use standard tools where possible; I prefer not to grow reliant on custom scripts and wrappers to an extent that I don't know how to live without them.

e.g. ls is aliased to ls --color on almost all systems. If you go to a machine without that alias, you'll live just fine.

aliasing git log to something entirely different would be a huge no-no for me, but simply enhancing its output to make my life a little easier is something I'm onboard with, yet not something I'd give up the muscle memory of typing git log for (e.g. if I created a git lg abbreviation).

[zanchey]

It's not terribly complex to do that kind of thing with a function:

function git
    if test -n "$argv[1]"
        switch $argv[1]
            case log
                command git log --graph $argv[2..-1]
            case '*'
                command git $argv[1..-1]
        end
    end
end

[faho]

Of course, @zanchey's proposal will fail if you have any other argument before the subcommand (e.g. git -C /some/path log). To make it bullet-proof, this would require something like __fish_git_needs_command in the git completions.

Which goes to show that making this work for arbitrary commands, just via alias "$command $subcommand"="$command $subcommand $options" is probably not going to work.

So we could either live with that limitation, or we could ask users to define a function.

Personally, I don't want to expand alias. I like it that fish has no special notion of aliases - it's all just functions. So I'd like it if alias stays for simple a=b type stuff, and functions or abbrs for more complicated things.

[faho]

@mqudsi: I don't think this is going to work, so I'm closing this. If you come up with a plan for how to do this, I'd be happy to talk about it. But as it stands, this would require that we do a commands argument parsing for it.