Mercurial Branch Repositories with SUBREPOS

Question

I'm trying to determine how people use "branch repositories" while also using subrepos.

Let's say I have repo Main containing a solution file (.NET), and populated with subrepos A, B, C:

/Main
    - A
    - B
    - C
    MainSolution.sln

A, B, and C, while being shared between other "Main" repos, are very tightly integrated into Main project. Thus, a major feature to the Main repo will require modifications to the subrepos (i.e., they are shared libraries, but are very actively developed).

Now it is time to add a feature. This feature is too big for one person to handle, and thus the code will need to be pushed to the central repo so others can help. We'd also need to be able to go back to the last "stable" code before the feature development began in case a bugfix is needed. I believe I have two options at this point: (1) create a named branch in the Main repo, or (2) create a new clone of Main. Since there are subrepos, both of these options have repercussions not present typically.

Option 1) Creating a named branch will, I presume, allow modifications to the subrepos to be committed/pushed, but only other people who have also updated to that branch in their clone of Main will be affected, since the .hgsubstate file is tracked. However, the subrepos will get a new head, and thus the (possibly) experimental feature would end up getting pushed to the central repo. Am I understanding this correctly?

Option 2) There are numerous advocates for the "don't use named branches, use 'branch repositories'", which are literally clones of the main repo, but named differently and existing on the central server. This is a little appealing to me, as it seems to keep things separated (and thus detached from disaster as co-workers --and myself!-- are still learning Mercurial). But this workflow seems completely broken when subrepositories are involved, since creating a clone of the Main repo does not create new, separated clones of the subrepos. It's a new clone, but it's still pointing at the same subrepos, and thus changes made to them will find their way back into the subrepos! I realize this is by design, and it's one of the really cool things (to me) about Mercurial. But how on earth do people use this branch repository workflow with subrepositories? It is completely inconceivable that, for each feature/experiment/version/whatever, I'm going to create a new clone (on the central server) of the Main repo, AND create clones (on the central server) of the subrepos, AND modify all the .hgrc/.hgsub paths to point to the proper central repos.

At this point, I'm just trying to understand HOW people work on a complicated project and use subrepos with branch repositories. Any thoughts?

Answer 1

You have other options as well. You could use bookmarks, for example. Since version 1.9, bookmarks can be pushed and pulled, they're not just local anymore. Since you often don't want a development "branch" to stick around as a named branch after that new feature is completed, bookmarks are often a better choice for that kind of thing. I tend to use bookmarks for new development and save real branches for released versions.

You should also be aware that subrepositories don't have to be shared between multiple main repositories in the way you describe. You can actually have the subrepositories stored inside a main repository (as opposed to having them at the same level as the main repos, or stored in some other location entirely), which would make them unique to each main repository, except you can push and pull from the subrepos in other main repos when you want to share those changes. This is the way I usually do it.

Unfortunately much of this is difficult to explain without a whiteboard, so please let me know if this isn't clear.

Answer 2

I prefer named branches for features that will most likely eventually get merged into the default branch. It is much easier to switch branches than switch repos.

With named branches you never need to worry about accidentally pushing your unstable branch of development into the stable repo. The named branch is already there, but won't be retrieved via an update unless a developer asks for it.