How do I push specific changesets to a shared library repo in Mercurial?

Question

I have a repo called MySharedLib, and another repo called MyProject. MySharedLib is included in many different repos by force-pulling (like a Jedi), and NOT using subrepos.

If you clone MyProject, you are left with the following structure:

/MyProject
    MySharedLib
    OtherStuff
    Files...

MySharedLib is not a subrepo. Pulling in changes from MySharedLib is as easy as running:

hg pull -f path/to/MySharedLib.

But if changes are made to /MyProject/MySharedLib, what's the most straightforward/standard way to push ONLY those changes to the MySharedLib repo?

MQ? hg export? hg diff? hg transplant? My understanding is that almost all of these options work (some together, some apart), but I'd like some direction.

And then what happens if a dev makes a commit that includes other files than those within MySharedLib? Obviously this is something to avoid, but I'm just curious.

Answer 1

Wow, what a bizarre setup. How do you prevent changes to MySharedLib from being pushed to MyProject? How do the files from MySharedLib ever appear unless you do a merge after pulling them? Once you do the merge, the repos are joined and you will need to make advanced used of hg convert (as described in this question about splitting repositories) to pull them apart again.

Do not do this. Use subrepos. This problem is what they exist to solve.

Answer 2

Here are the constraints that govern what you can push:

• you can only push whole changesets -- if you commit some changes together it's all or none on the pushing front, you can't break up a changeset after you commit it
• you can't push a changeset without pushing all of it ancestor changesets to

So once you've committed a linear history like this:

[0]---[1]----[2]-----[3]

you can push changesets zero and one without pushing two and three, but if you want to push two you also have to push zero and one.

And if changeset one contains changes to both /MyProject/OtherStuff and /MyProject/MySharedLib/ you have to push those together.

Your only flexibility comes before you commit where you can control:

• what goes into a changeset
• what the parents of a changeset are (which also have to be pushed with it)

So if your history currently looks like this:

[0]---[1]

and hg status is showing something like this:

M MyProject/OtherStuff/file1
M MyProject/OtherStuff/file2
M MyProject/MySharedLib/file3
M MyProject/MySharedLib/file4

Then you want to make a new changeset that has only the changes for MySharedLib that you want to push:

hg commit --include MyProject/MySharedLib

making your history look like:

[0]----[1]-----[2]

and then, before you commit the changes in OtherStuff you don't want to push you do a hg update to change the current parent revision so that your new changeset will have a parent of one instead of two:

hg update 1

Now when you do:

hg commit

your new changeset, three, will have only the non-MySharedLib changes and a parent of one, so you history will look like this:

[0]-----[1]--------[2]
          \
           --------[3]

Since two and three aren't one another's ancestors you can push either one without pushing the other.

That said, omnifarious is right: your usage isn't just weird, it's out and out wrong. You should look at a subrepo setup. It almost certainly achieves your goals better than what you or I have just described.