Improve API to get flag completion function (#2063)

The new API is simpler and matches the `c.RegisterFlagCompletionFunc()`
API.  By removing the global function `GetFlagCompletion()` we are more
future proof if we ever move from a global map of flag completion
functions to something associated with the command.

The commit also makes this API work with persistent flags by using
`c.Flag(flagName)` instead of `c.Flags().Lookup(flagName)`.

The commit also adds unit tests.

Signed-off-by: Marc Khouzam <marc.khouzam@gmail.com>

Update main image to better handle dark background (#1883)

Fixes #1880

Signed-off-by: Marc Khouzam <marc.khouzam@gmail.com>
Co-authored-by: Deleplace <deleplace2015@gmail.com>

Check for group presence after full initialization (#1839) (#1841)

Fixes #1831

By moving the check for help group existence to "ExecuteC()" we no
longer need groups to be added before AddCommand() is called.  This
provides more flexibility to developers and works better with the use
of "init()" for command creation.

Signed-off-by: Marc Khouzam <marc.khouzam@gmail.com>

Signed-off-by: Marc Khouzam <marc.khouzam@gmail.com>
Co-authored-by: Marc Khouzam <marc.khouzam@gmail.com>

feat: make InitDefaultCompletionCmd public (#1467)

* feat: make InitDefaultCompletionCmd public

* PR comments

* Update man_docs_test.go

* Update README.md

Bump golangci/golangci-lint-action from 3.1.0 to 3.2.0 (#1697)

Bumps [golangci/golangci-lint-action](https://github.com/golangci/golangci-lint-action) from 3.1.0 to 3.2.0.
- [Release notes](https://github.com/golangci/golangci-lint-action/releases)
- [Commits](golangci/golangci-lint-action@v3.1.0...v3.2.0)

---
updated-dependencies:
- dependency-name: golangci/golangci-lint-action
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Removes viper dependency by removing cobra/ CLI tool (#1604)

The cobra bootstrapping CLI tool has moved to
https://github.com/spf13/cobra-cli

Signed-off-by: John McBride <jmcbride@vmware.com>

Bump github.com/spf13/viper from 1.9.0 to 1.10.0 (#1561)

Bumps [github.com/spf13/viper](https://github.com/spf13/viper) from 1.9.0 to 1.10.0.
- [Release notes](https://github.com/spf13/viper/releases)
- [Commits](spf13/viper@v1.9.0...v1.10.0)

---
updated-dependencies:
- dependency-name: github.com/spf13/viper
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Fix flag completion (#1438)

* Fix flag completion

The flag completion functions should not be stored in the root cmd.
There is no requirement that the root cmd should be the same when
`RegisterFlagCompletionFunc` was called. Storing the flags there does
not work when you add the the flags to your cmd struct before you add the
cmd to the parent/root cmd. The flags can no longer be found in the rigth
place when the completion command is called and thus the flag completion
does not work.

Also #1423 claims that this would be thread safe but we still have a map
which will fail when accessed concurrently. To truly fix this issue use a
RWMutex.

Fixes #1437
Fixes #1320

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

* Fix trailing whitespaces in fish comp scripts

Signed-off-by: Paul Holzinger <pholzing@redhat.com>

Fix documentation (#1434)

Signed-off-by: Marc Khouzam <marc.khouzam@montreal.ca>

Fix typo