Mercurial repository narrow clone?

Question

Update because of new insights : Upon seeing this question five years later, I realise that this stems from trying to use a version control system as a package manager. This of course leads to all sorts of unexpected issues, and we shouldn't be using it that way. If you're reading this question, I suggest searching for a package manager for your preferred language.

My original question : I'm currently in the process of moving from Subversion to Mercurial, and I have to say I don't regret that decision. However, when trying to convert my project, I ran into a problem of Mercurial, which I can't seem to get fixed. I have two distinct projects: one is a framework, and the other is an application that relies on that framework. Here's what the repositories look like:

The Framework repository:

• docs/
• deploy/
• lib/
• tests/

The Application repository:

• application/
• config/
• lib/
• tests/
• www/

What I'd like is for the application's lib directory to contain a copy of the frameworks' lib/ directory. I used to do this using svn:externals. Now, I am aware that Mercurial supports the concept of subrepositories , but that doesn't seem like the "correct" solution, as it doesn't actually pull in the lib/ directory like I wanted, as you'll still have to pull and push changes manually . That, plus once you clone the framework repository, you'll get all of it, not just the lib/ directory. I only need the lib/ directory, not the tests, or the docs.

Now, I thought up two different solutions to this problem, but I wonder which is the best. The first solution would be to clone the framework in a different directory altogether and create symlink in the application's lib/ directory which points to the framework's lib/ directory. Putting the symlink in .hgignore should make sure all is well, I think? That means that you could edit the frameworks code, and commit that, and you could edit the application's code and commit that, too.

The other option is to have multiple repositories. The framework gets pulled as a whole, which means you'll get the docs/, deploy/, test/ etc. directories, which are not needed for usage of the framework. I thought maybe creating a repository purely for the library might be a solution, although I sincerely doubt it, as the Unit Tests are very dependant upon the library itself.

Does anyone know a decent solution for this problem?

Answer 1

You should separate out the libraries into a separate repository if you need to refer to only that.

Provided you actually do need to only refer to that. What is the problem with referring to the repository containing the lib directory + other stuff, other than "it doesn't feel right"?

As for "still have to pull and push manually", when you pull your main clone, it'll pull the subrepos as well, but it won't update them to a newer revision, which is a good thing, you need to do that manually, just as you should with Subversion.

Answer 2

You should put separate components in their own repositories. Then, when you create an application, you can use the convert extension to create a pullabale framework repository out of the normal one:

$ hg convert --filemap map.txt framework new-framework

with map.txt containing the renames/includes/excludes (the following one should only include the lib directory and move everything in there to the repository root):

include lib
rename lib .

From the application repo, you can now just pull the framework repo (use -f the first time, since the repositories will likely have nothing to do with each other).

$ cd project
$ hg pull -f ../new-framwork
$ hg merge

Now, when the development goes on, you just have to re-create the converted repo every time before you pull and you're good to go. We actually have a hook on our framework repository that re-creates the converted repo on every changegroup (= every push).

This way you have both work areas (app and framework) in their own repositories, while the app repo contains the complete framework history and is able to be updated by simply pulling from the converted repo.