TutorialMerge

["Tutorial"] - Merging changes

In TutorialExport, we learned how to share a change with another person. But, since (as of version 0.6c anyway) ["Import"] isn't yet functional enough to handle merges correctly, we're going to demonstrate merging by pulling from another repository that has made an incompatible change.

First, we must create a reason to merge. Let's ["Clone"] the my-hello repository again:

 $ cd ..
 $ hg clone my-hello my-hello-desc

We are going to give hello.c a description in its comment section.

 $ cd my-hello-desc
 $ vi hello.c

Let's change the second line from this:

 * hello.c

To this:

 * hello.c - hello, world

Let's save and quit the editor, and ["Commit"] our change. This time, we save a few moments by using the -m option to the commit command, to save us from being dropped into another editor:

 $ hg commit -m'Add description of hello.c'

At this point, we have made one change to hello.c in the my-hello-new-output ["Repository"], and another change to hello.c in the my-hello-desc ["Repository"]. Will there be a problem when we want to pull from one into the other?

This works just fine. While still in my-hello-desc, let's ["Pull"] those changes from my-hello-new-output and see what happens:

 $ hg pull ../my-hello-new-output
 pulling from ../my-hello-new-output/
 searching for changes
 adding changesets
 adding manifests
 adding file revisions
 modified 1 files, added 1 changesets and 1 new revisions
 (run 'hg update' to get a working copy)

This looks just like the output of pull from TutorialShareChange! So all we have to do is an ["Update"] now, right?

 $ hg update
 this update spans a branch affecting the following files:
  hello.c (resolve)
 aborting update spanning branches!
 (use update -m to perform a branch merge)

Something has happened. ["Mercurial"] is telling us that we must ["Merge"] the changes that we made in each ["Repository"]. This sounds painful, right?

It's actually very easy. We simply follow the instructions:

 $ hg update -m
 merging hello.c

And that's all there is to it; ["Mercurial"] was able to handle the merge completely automatically. If we look at hello.c now, we find that it contains /both/ the change from my-hello-new-output and the change from my-hello-desc.

Much of the time, when you are working with changes made by other people, this is the /only/ kind of merge you will need to perform.

Let us continue on, and learn how to deal with situations where conflicting changes have been made, in TutorialConflict.