repo exclusion: switch to dynamic rule builder

[mrnugget]

This is a follow-up to https://github.com/sourcegraph/sourcegraph/pull/58377 and changes how exclude works by AND'ing all conditions in a single rule together.

It does this mostly by refactoring the code and turning things upside down (inside out?):

• instead of each []exclude entry in a code host connection config being turned into a separate condition, one of which had to be true
• each entry is turned into a *rule that can have multiple conditions and all of them have to be true for a repo to be excluded.

Best explained with an example.

Old code:

var eb excludeBuilder
for _, r := range c.Exclude {
  eb.Exact(r.Name)
  eb.Exact(r.Id)
}
exclude, err := eb.Build()
if err != nil {
  return nil, err
}

// then:

exclude(r.Id) || exclude(r.Name) || exclude(r)

New code:

var ex repoExcluder
for _, r := range c.Exclude {
  ex.AddRule().
    Exact(r.Name).
    Exact(r.Id)
}
if err := ex.RuleErrors(); err != nil {
  return nil, err
}

// then:

ex.ShouldExclude(r.Id) || ex.ShouldExclude(r.Name) || ex.ShouldExclude(r)

Comparison not totally fair because stil need to add error handling for invalid patterns.

Downsides

Currently it's a lot more function calls per exclusion-check... we could probably amortize the cost but I'm not sure yet what the nicest way is.

Test plan

• unit tests, extended

[eseliger]

wonder if it would be nice to encapsulate the excluder in a separate package, and then implement this special excludeFn in the github source file, I stumbled a bit over the fact that there's a github specific implementation in this otherwise quite generic file. Not needed for this PR.

[mrnugget]

Yeah. I keep thinking about this. I haven't solved the puzzle yet. I have an idea for all the "rules" to compile down to this, but I still need to play around with the ideas a bit.

[sourcegraph-bot]

Codenotify: Notifying subscribers in CODENOTIFY files for diff 000a43e...1f90a29.

Notify	File(s)
@eseliger	internal/repos/awscodecommit.go internal/repos/azuredevops.go internal/repos/bitbucketcloud.go internal/repos/bitbucketserver.go internal/repos/exclude.go internal/repos/exclude_test.go internal/repos/github.go internal/repos/gitlab.go internal/repos/gitolite.go internal/repos/other.go internal/repos/sources_test.go