Change compare URLs programatically (in bulk)

[rcmachado]

In a scenario where you migrate the project from one repository provider to another (eg. Bitbucket to GitHub) or even renaming the project, would be nice to automatically change the compare links for each version. Something like:

$ changelog fmt --compare-url "https://example.com/{{.PreviousVersion}}-{{.CurrentVersion}}"

This would reformat the changelog file, updating all the compare URLs using the new template.

(Stolen from olivierlacan/keep-a-changelog#249)