configfile: Initialize nil AuthConfigs

[Danial-Gharib]

• Fixes: Nil pointer dereference on loading the config file #4414

- What I did

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- Description for the changelog

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[bsousaa]

Thank you for contributing! It appears your commit message is missing a DCO sign-off,
causing the DCO check to fail.

We require all commit messages to have a Signed-off-by line with your name
and e-mail (see "Sign your work"
in the CONTRIBUTING.md in this repository), which looks something like:

Signed-off-by: YourFirsName YourLastName <yourname@example.org>

There is no need to open a new pull request, but to fix this (and make CI pass),
you need to amend the commit(s) in this pull request, and "force push" the amended
commit.

Unfortunately, it's not possible to do so through GitHub's web UI, so this needs
to be done through the git commandline.

You can find some instructions in the output of the DCO check (which can be found
in the "checks" tab on this pull request), as well as in the Moby contributing guide.

Steps to do so "roughly" come down to:

1. Set your name and e-mail in git's configuration:

   git config --global user.name "YourFirstName YourLastName"
   git config --global user.email "yourname@example.org"

   (Make sure to use your real name (not your GitHub username/handle) and e-mail)

2. Clone your fork locally

3. Check out the branch associated with this pull request

4. Sign-off and amend the existing commit(s)

   git commit --amend --no-edit --signoff

   If your pull request contains multiple commits, either squash the commits (if
   needed) or sign-off each individual commit.

5. Force push your branch to GitHub (using the --force or --force-with-lease flags) to update the pull request.

Sorry for the hassle (I wish GitHub would make this a bit easier to do), and let me know if you need help or more detailed instructions!

[vvoland]

Thank you for the contribution!
In addition to the missing DCO, I have one suggestion.

[vvoland]

This won't save the auth in the ConfigFile because we create a completely new map here.

Instead of doing the nil check on caller side, we need to solve this issue in the GetAuthConfigs directly:

cli/cli/config/configfile/file.go

Lines 95 to 98 in df04aca

	// GetAuthConfigs returns the mapping of repo to auth configuration
	func (configFile *ConfigFile) GetAuthConfigs() map[string]types.AuthConfig {
	return configFile.AuthConfigs
	}

This way we also won't have to do the nil check in all the places GetAuthConfigs is called (there are currently no other places which break with nil value though).

[codecov-commenter]

Codecov Report

Merging #4418 (9a4552d) into master (803d4a9) will increase coverage by 0.43%.
The diff coverage is 40.00%.

❗ Current head 9a4552d differs from pull request most recent head ad43df5. Consider uploading reports for the commit ad43df5 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #4418      +/-   ##
==========================================
+ Coverage   58.97%   59.40%   +0.43%     
==========================================
  Files         286      288       +2     
  Lines       24771    24780       +9     
==========================================
+ Hits        14608    14721     +113     
+ Misses       9276     9173     -103     
+ Partials      887      886       -1     

[vvoland]

I went ahead and applied my suggestion as we'd like to get this in for the next patch release.

[thaJeztah]

LGTM

we should look at some of the follow-ups as well, but this fixes the immediate issue