This commit fixes#119. Summary:
- Depend on packaging to get a good implementation of PEP 440.
- Document new behaviors.
- Add support for migrations.
- Checkout by default the most modern git tag available in the template.
- Reuse `run_tasks` to run migrations too.
- Use `git describe --tags --always` to obtain template commit, to get a version parseable by PEP 440.
- Update `test_updatediff` to with new behaviors.
@Tecnativa TT20357
Fix#88 the easiest way possible. Changes summary:
- A new `--vcs-ref` flag that indicates which commit/ref you want to copy, and only applies when the source directory is git-versioned.
- A new `--no-diff` flag to `copier update` skips the smartypants diff behavior.
What it does?
- Checks you are updating a git-versioned destination from a git-versioned source.
- Clones the destination into temp dir.
- Does a `copier copy -f tmp_src tmp_dst` (yes, a temp dir also).
- Gets the git diff between `tmp_dst` and `dst_path`.
- Performs a normal `copier update dst_path`.
- Applies the git diff at the end, to try to respect downstream project evolution.
@Tecnativa TT20357
