Publishing: Improve diff comparison when on custom branch

[MariusStorhaug]

Change

Fix the publishing logic, so it works as expected in different scenarios. When doing prerelease in custom branch, it now compares whole content of the branch with the main/master branch to determine if a change has happened on a module. Old logic required a change to be on the last commit.

Behavior when running on custom branch with multiple commits where first commit was a change on version file for shares:

GitHub:
https://github.com/MariusStorhaug/ResourceModules/runs/5413150374?check_suite_focus=true#step:4:243

ADO:

Behavior when merging after a PR:

GitHub:
https://github.com/MariusStorhaug/ResourceModules/runs/5413219475?check_suite_focus=true#step:4:243

ADO:

Type of Change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update (Wiki)

Checklist

• I'm sure there are no other open Pull Requests for the same update/change
• My corresponding pipelines / checks run clean and green without any errors or warnings
• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (readme)
• I did format my code