Improve tracing possibilities to diagnose issues

[Silvanoc]

I'm running copier copy on a template that was working. Now I'm changing some things in the template, apparently some old answers are being reused and I'm failing to understand which old answers are being used. I cannot find the file with the previous answers in the documented paths.

I would expect the possibility to give a flag like --debug so that I can get an output like:

reading answers file from XYZ
reading template xyz
replacing field ABC
reading template abc

[benjamin-schilling]

I also have some questions in a template, copier is not asking for answers for. It would be great to be able to understand where copier takes answers from.

[benjamin-schilling]

Off-topic for this discussion thread, but:

https://copier.readthedocs.io/en/stable/generating/#copying-dirty-changes

says

If you use a local clone of a template repository that has had any uncommitted modifications made, Copier will use this modified working copy of the template to aid development of new template features.

while

https://copier.readthedocs.io/en/stable/faq/#while-developing-why-doesnt-the-template-include-dirty-changes

says:

Now, if you copy that template into a folder like this:

$ copier copy ./src ./dst
... you'll notice there's no new-file.txt. Why?

Well, Copier indeed included that into the HEAD ref. However, it still selected v2.0.0 as the ref to copy, because that's what Copier does.

Or am I missing something?

[sisp]

I think Copier behaves exactly as documented:

mkdir src/
pushd src/
git init
echo 'question: foo' > copier.yml
echo '{{ question }}' > result.txt.jinja
git add .
git commit -m v1
git tag v1
echo 'question: bar' > copier.yml
popd

uvx copier copy --defaults src/ dst1/
cat dst1/result.txt # -> foo

uvx copier copy --defaults --vcs-ref HEAD src/ dst2/
cat dst2/result.txt # -> bar

The dirty state of the template repository is only used when passing --vcs-ref HEAD, else the latest tag is used.

[Silvanoc]

We are trying to develop a template and running from a dirty state without --vcs-ref we see following message:

/opt/homebrew/Cellar/copier/9.13.1/libexec/lib/python3.14/site-packages/copier/_vcs.py:209: DirtyLocalWarning: Dirty template changes included automatically.
  warn(

But not the dirty state (what we except), but the latest tag is being used (ignoring that way my local changes).

Additionally it looks as if a warning should be shown, but it's failing to show it.

[sisp]

A few years ago, there was a bug report (#787) related to including dirty changes in HEAD which led to a fix (#1047) where the behavior was also documented. I've gone over these discussions and changes, I think the current behavior is intended, but the warning is misleading because it suggests that dirty changes are included in the template revision from which the project will be generated, while in fact the changes are only included in the local template repo's HEAD which will not be used if there is a version tag or --vcs-ref HEAD is passed. I'll fix the behavior to raise the warning only if no version tags exist or --vcs-ref HEAD is passed.

[sisp]

I've created a PR that raises the warning only when dirty changes are actually included: #2547