GitLab

* Staticcheck fixes

This fixes all staticcheck warnings for this library.

- first step toward implementing file ignore

feat(file-ignore): implement file ignore

- add flags for providing a gitignore and/or list of files to ignore
- construct a filter to be passed to a SerialFile

feat(file-ignore): use go-ipfs-files fork; use renamed constructor

feat(file-ignore): test case w. ignore rules; refactor parseArgs

feat(file-ignore): ignore-rule opt is open-ended

- make ignore-rules options accept a path to a file
- add test case for ignore rules file

feat(file-ignore): help-text for variardic opts

- show StringsOption as variardic option in help-text
- add test case for variardic option

feat(file-ignore): rename rulesfile opt; fix typos

feat(file-ignore): temp replace of go-ipfs-files

- temporarily using go-ipfs-files fork until go-ipfs-files#26 is merged
- trying to get ci/cd builds working
- will revert before merging

feat(file-ignore): refactor cli/parse.go#setOpts

feat(file-ignore): cleanup parse.go; add test-case

feat(file-ignore): update ignore option copytext

feat(file-ignore): check opt against `optDef.Type`

- revert exclusion of options with `Strings` type,
so those option values are typechecked
- add command test cases

feat(file-ignore): add test-case w. hidden file

feat(file-ignore): build against go-ipfs-files@latest

feat(file-ignore): update go.mod/go.sum

- remove HandleError() because we now have CloseWithError
- remove Header interface
- remove all Head() methods
- fix locking in chan.go
- use EmitChan in ResponseEmitters
- introduce cmds.ErrClosedEmitter
- fix tests (some still expected errors to be emitted/marshaled)

to func(Response, ResponseEmitter) error

Apparently, it's not thread-safe.

**Returning errors/calling:**

Instead of having a dance where we:
  * Close the response emitter immediately if the command succeeds.
  * Return an error, call SetError, and then close the response emitter if it
    fails.

Just set the error from within the `Call` command and always close the response
emitter.

**Doner**

Get rid of the Done channel/doner interface from the response emitter. We close
the response emitter after finishing the Call *anyways* so this channel isn't
necessary (anymore, at least).

We *always* expect environments to be able to return a context so we might as
well enforce this with the type system.

These aren't placeholder contexts.

This is the best place for inserting it that I found.

Test in #2648 should be modified to run `Root.ProcessHelp()`.

License: MIT
Signed-off-by: Jakub Sztandera <kubuxu@protonmail.ch>