Add support for fish completion

[sayboras]

Add completion support for fish shell

[bombsimon]

LGTM!

[iwankgb]

Mention golangci/team when your Cobra PR is merged.

[sayboras]

@golangci/team seems like cobra might take time to release tagged version, just wanna check if you guys are ok with git hash version from master. If yes, I can merge this in, otherwise, will mark this as draft.

[Alwayswithme]

@sayboras hi, I generate completion script at this directory by golangci-lint completion fish > ~/.config/fish/completions/

but encouter issue when golangci-lint run <hit tab>, can u teach me how to setup completion for fish?

➜  completions golangci-lint run math: Error: Unexpected token
'ompletion ended with directive: ShellCompDirectiveDefault / 1'
         ^
math: Error: Unexpected token
'% 2'
 ^
test: Missing argument at index 2

~/.config/fish/completions/golangci-lint.fish (line 99): 
    if test $compErr -eq 1
       ^
in function '__golangci_lint_prepare_completions'
in command substitution

(Type 'help test' for related documentation)
math: Error: Unexpected token
'ompletion ended with directive: ShellCompDirectiveDefault / 8'
         ^
math: Error: Unexpected token
'% 2'
 ^

golangci-lint has version 1.33.0 built from b90551c on 2020-11-23T06:54:06Z
fish, version 3.1.2

[sayboras]

have you try with ~/.config/fish/completions/golangci-lint.fish ?

tam.mach@24430 ~/g/s/g> golangci-lint
cache  (Cache control and information)  help                                                                                                (Help)  version  (Version)
completion  (Output completion script)  linters                                                               (List current linters configuration)
config                        (Config)  run  (Run this tool in cloud on every github pull request in https://golangci.com for free (public repos))

tam.mach@24430 ~/g/s/g> golangci-lint version
golangci-lint has version 1.33.0 built from b90551c on 2020-11-23T06:54:06Z