Add 'tag_pattern' feature to git dependencies

[sigurdm]

Re: #1250

With this proposal you can use a git repo as a versioned package repository.

For example write:

dependencies:
  foo:
    git:
      url: https://github.com/foo/foo
      tag_pattern: v*
    version: ^2.0.0

And all commits in the git repo that are tagged according to v* will be inspected. If they contain a pubspec.yaml with name: foo they will be considered for resolution.

The tag_pattern syntax is the one used by git tag --list. See https://git-scm.com/docs/git-tag#Documentation/git-tag.txt---list

This feature is explicitly opt-in:

• any git dependency without a tag_pattern retain the existing behavior.
• The depending pubspec need to be at least at version 3.7.0

Open questions:

• Should we forbid mixing the two kinds (ref-based and tag_pattern-based) of git-dependencies within a single resolution?
• ...

[jonasfj]

Just wondering, if we should support multiple patterns, and if we should then default to two:

            tagPatterns = ['v*', '$package-v*'];

[sigurdm]

Hmm - considering this again I think we should actually not default to anything. I think it is probably better to be unopinionated here

[jonasfj]

Should we use tag-pattern for consistency? (it would be inconsistent with other fields in pubspec.yaml).

[sigurdm]

Hmm - this is pubspec.lock.
In pubspec.yaml we use _ (at least in pubspec_overrides and dev_dependencies.

So when we copy the field from the pubspec.yaml to pubspec.lock it is confusing if we change the spelling.

At the same time it is confusing that we have resolved-ref in the pubspec.lock.

Can we find a single-word alternative?

[jonasfj]

What about simply using tags and then support one or more patterns?

dependencies:
  foo:
    git:
      url: https://foo.bar.git/repo
      tags: v*

and

dependencies:
  foo:
    git:
      url: https://foo.bar.git/repo
      tags:
       - v*
       - foo-v*

or maybe not.

[sigurdm]

Yeah - that might work