feat: add 'branches' git tag variant

[snickell]

Fixes: #6989

Description
Implements a new git tagpolicy variant Branches, which can be used as follows:

tagPolicy:
  gitCommit:
    variant: 'Branches'

When this tagPolicy is active, when currently tracking a git branch, the branch's name (git branch --show-current) with slashes replaced with underscores will be used as the tag, otherwise the current short sha commit will be used.

[codecov]

Codecov Report

Merging #7006 (15600c3) into main (290280e) will decrease coverage by 1.76%.
The diff coverage is 56.96%.

❗ Current head 15600c3 differs from pull request most recent head be55c28. Consider uploading reports for the commit be55c28 to get more accurate results

@@            Coverage Diff             @@
##             main    #7006      +/-   ##
==========================================
- Coverage   70.48%   68.71%   -1.77%     
==========================================
  Files         515      554      +39     
  Lines       23150    25698    +2548     
==========================================
+ Hits        16317    17659    +1342     
- Misses       5776     6834    +1058     
- Partials     1057     1205     +148     

Impacted Files	Coverage Δ
cmd/skaffold/app/cmd/deploy.go	52.00% <ø> (-1.85%)	⬇️
cmd/skaffold/app/cmd/dev.go	84.61% <0.00%> (ø)
cmd/skaffold/app/cmd/render.go	36.66% <0.00%> (-4.72%)	⬇️
cmd/skaffold/skaffold.go	0.00% <0.00%> (ø)
cmd/skaffold/app/cmd/inspect_tests.go	62.50% <14.28%> (-1.14%)	⬇️
cmd/skaffold/app/cmd/lsp.go	28.12% <28.12%> (ø)
cmd/skaffold/app/cmd/fix.go	68.85% <40.00%> (-7.62%)	⬇️
cmd/skaffold/app/cmd/lint.go	42.85% <42.85%> (ø)
cmd/skaffold/app/cmd/find_configs.go	48.88% <50.00%> (+0.24%)	⬆️
cmd/skaffold/app/skaffold.go	76.19% <70.00%> (-8.43%)	⬇️
... and 177 more

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[gsquared94]

lgtm, except one typo and one good to have testcase.

[snickell]

I'm trying to figure out why the linter check is breaking here:

Error: pkg/skaffold/tag/git_commit_test.go:761:48: (*gitRepo).branch - result 0 (*github.com/GoogleContainerTools/skaffold/pkg/skaffold/tag.gitRepo) is never used (unparam)
make: *** [Makefile:126: linters] Error 1
func (g *gitRepo) branch(newBranchName string) *gitRepo {

Unfortunately this is my first go PR, I can't quite see how branch() is referencing *gitRepo (or not) any differently than the parallel functions like commit()..... could somebody with more go experience take a look and suggest?

[snickell]

Oh I see, its that nothing is (currently) using the *gitRepo typed return value of branch(), because its always the last in our existing tests. I'm adding a no-op .commit('second') after one of the branches to provide a ref and please the linter.

[snickell]

OK, I think this might be ready for merge pending review by @tejal29

[snickell]

@gsquared94 Do the schemas need manual editing to add the branch tag policy, or is that something that's automatically done on the skaffold build system side?

[snickell]

Aloha @gsquared94 / @briandealwis , I was wondering if my PR not editing the schemas was a mistake? Or are schemas going to update automatically at some point?

[briandealwis]

@snickell the schemas and the docs will need to be updated separately.

[snickell]

OK, I'll open a separate PR for that, sorry I thought those might be auto-generated by a github action or something, my bad!