(Breaking change) chore: change default target-branch to main

[fty4]

What this PR does / why we need it:

Because the default branch on GitHub is main and not longer master this should also be the default to chart-testing.

Which issue this PR fixes:

fixes #376

Special notes for your reviewer:

BREAKING CHANGE:
If e.g an action or workflow is not using an explicit specified target-branch the job might will fail after this change.

But after this change new users does not have the problem that a wrong branch is used.
For example I was suffering with the error message exit status 128- see #330 because the default branch was not main.

[thisisrachelramos]

[cpanato]

@fty4 can you rebase and update the docs? thanks for this PR

[fty4]

@cpanato I've updated the docs and forced-pushed the rebased commits.
_{^{(Required multiple force-push because of DCO)}}

[cpanato]

this will be a breaking change for existing users, if they dont set the --target-branch in the config

[fty4]

That is true - I already mentioned this in the PR body.

New users will still have to specify the parameter if this will not be changed.

[cpanato]

when we release I will make a note in the release notes for this

[cpanato]

small request

[odysseu]

LGTM 👍

[jouve]

this can be tested here with

• use the same ref to check branch existance and merge-base calculation #601
• use .helmignore when identifying changed charts #591
• (Breaking change) chore: change default target-branch to main #510
• fix(lint): honor the --since flag when checking for version increment #508

[github-actions]

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[cpanato]

lgtm

[davidkarlsen]

Lgtm. We can maybe bump version number a bit to signal breaking change.

[cpanato]

Lgtm. We can maybe bump version number a bit to signal breaking change.

yes

[cpanato]

let marinate this in the main branch for a while