Support Main CI tools out of the box

[arnaud-deprez]

Is your feature request related to a problem? Please describe.

Given most CI tools do git fetch in detached mode, gsemver cannot directly inspect what is the current branch. Instead you can set an environment variable GIT_BRANCH to let gsemver knows which branch it should use to match against a bumpStrategy.

Describe the solution you'd like

As most CI tools provides the current branch context in some environment variables, it is possible to determine in which CI tool the build is running and then get the correct branch information from env variables.

Out of my head CI tools to support:

• [ ] github actions
• [ ] gitlab ci
• [ ] bitbucket
• [ ] jenkins
• [ ] azure pipeline
• [ ] aws codebuild
• [ ] google cloud build
• [ ] Other CI tools ?

GIT_BRANCH should still be used as a fallback solution for the not yet supported CI tools.