Add support for multiple semver tags

[fastlorenzo]

This PR relates to issue #6

If full-semver input is set to true, the action will try to parse the version tag (using semver package) and extract the major, minor, patch and prerelease components.

Example for input tag v1.2.3-beta.4, the following tags will be added:

• v1
• v1.2
• v1.2.3

Note that to add the prefix (v in this case), the following input option has been added as well: semver-prefix (in this case, it is equal to v)

[codecov]

Codecov Report

Merging #10 into master will increase coverage by 1.15%.
The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master      #10      +/-   ##
==========================================
+ Coverage   71.21%   72.36%   +1.15%     
==========================================
  Files           3        3              
  Lines          66       76      +10     
  Branches       14       16       +2     
==========================================
+ Hits           47       55       +8     
  Misses          6        6              
- Partials       13       15       +2     

Impacted Files	Coverage Δ
src/context.ts	92.30% <ø> (ø)
src/meta.ts	74.07% <80.00%> (+1.34%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update dd2e615...c527b1b. Read the comment docs.

[crazy-max]

v2, v2.0 and v2.0.8 tags should not be generated for pre-release. As explained in semver specification prerelease versions are updated frequently, and contain many breaking changes that are (by the author's design) not yet fit for public consumption.

[crazy-max]

Suggested change

	fullSemver: /true/i.test(core.getInput('full-semver') || 'false'),
	fullSemver: /true/i.test(core.getInput('full-semver')),

[crazy-max]

And also update the relevant documentation.

[crazy-max]

@fastlorenzo I thought a little bit more about the implementation and I think we should go through templating instead. I had been working on this via #3 and I think I'll put it back for your use case. The idea will be to improve this feature by using a list of versions that you want to assign as tags:

-  
  name: Docker meta
  uses: crazy-max/ghaction-docker-meta@v1
  with:
    images: name/app
    tag-semver: |
      v{{major}}
      v{{major}}.{{minor}}
      v{{major}}.{{minor}}.{{patch}}

[fastlorenzo]

Looks good to me as well, but what does it do when ref is not a valid semver (for example, using the same action to build container for a tag or for a push in a branch)?

[crazy-max]

@fastlorenzo Will do nothing if it's not a valid semver.

[fastlorenzo]

@fastlorenzo Will do nothing if it's not a valid semver.

ok then I guess we can close this PR and go with your solution using tag-semver 😄