Updating a subproject within an existing Git repo

[flippedAben]

I have a Git repo at ~/repo. I have another Git repo at ~/my_copier_template. I tell copier to use ~/my_copier_template to generate a subproject at ~/repo/path/to/S (call it S for short). I track my new subproject in ~/repo by adding and committing the changes.

When I try to update S, it fails at:

copier/copier/main.py

Lines 607 to 610 in b8ff4d8

	if self.subproject.vcs != "git":
	raise UserMessageError(
	"Updating is only supported in git-tracked subprojects."
	)

This is because copier assumes that a subproject is tracked by Git if and only if it is in the root of a git repo, as stated here:

copier/copier/subproject.py

Lines 77 to 80 in b8ff4d8

	def vcs(self) -> Optional[VCSTypes]:
	"""VCS type of the subproject."""
	if is_git_repo_root(self.local_abspath):
	return "git"

But, S is not at the root of ~/repo. I would like to change copier to support this scenario, but wanted to get some thoughts before proceeding.

Part of the change will involve changing how we update:

copier/copier/main.py

Lines 670 to 673 in b8ff4d8

	git("fetch", "--depth=1", "real_dst", "HEAD")
	diff_cmd = git["diff-tree", "--unified=1", "HEAD...FETCH_HEAD"]
	try:
	diff = diff_cmd("--inter-hunk-context=-1")

How do we feel about not doing the fetch, and doing a git diff between R:/path/to/S and the cleanly generated T, instead of git diff-tree.

[bburgin]

+1 for this request.

We want to use copier on a repo with multiple answer files in subfolders. Also, we want to use copier on a large monorepo, but the fetch that copier does for this case is too slow.

[yajo]

This is a known problem, but I just noticed I never opened the proper issue for that. Done now: #450

[yajo]

Hi there, all you need to do is put your copier.yaml in the git root and add _subdirectory: repo/path/to/S.

Docs: https://copier.readthedocs.io/en/latest/configuring/#subdirectory (beware: docs for master, this feature changed from latest v5.x)

[flippedAben]

Ah, hold on. There seems to be a misunderstanding. I apologize for the poor wording.

R is a Git repo, but it does not hold copier templates. It holds Python source code only, let's say. R is where my generated subproject lives. T is a different Git repo that contains only my copier templates. Within T, I already have a copier.yaml that has _subdirectory: path/to/S. The problem is that when I want to update my generated subproject, copier doesn't think my subproject is tracked by a Git repo. But, it is tracked because I committed it to R.

I'll edit my initial post to be more clear.

[yajo]

Ah, I get your point now.

Ok this seems a valid usage, but indeed not supported yet. I opened #451 to track it.

PR wellone! 😁

[bburgin]

I put a PR up here #452

[bburgin]

Here's a different PR #453 that better aligns with the copier design and usage.