Question

I’ve only just started to use Git and think it is wonderful, however I’m a little confused over what the merge command does.

Let us say we have a working project in the branch "A".

I go home and make changes to this branch and save it as "B".
Another programmer makes changes to "A" and saves it as "C".

Is there a way to merge the two branches "B" and "C" together, then commit the changes as a new branch, say "D"?

Or am missing the point of ‘merge’?

Answer 1

merge is used to bring two (or more) branches together.

A little example:

$ # on branch A:
$ # create new branch B
$ git checkout -b B
$ # hack hack
$ git commit -am "commit on branch B"

$ # create new branch C from A
$ git checkout -b C A
$ # hack hack
$ git commit -am "commit on branch C"

$ # go back to branch A
$ git checkout A
$ # hack hack
$ git commit -am "commit on branch A"

So now there are three separate branches (namely A B and C) with different heads.

To get the changes from B and C back to A, checkout A (already done in this example) and then use the merge command:

$ # create an octopus merge
$ git merge B C

Your history will then look something like this:

…-o-o-x-------A
      |\     /|
      | B---/ |
       \     /
        C---/

If you want to merge across repository/computer borders, have a look at git pull command, e.g. from the PC with branch A (this example will create two new commits):

$ # pull branch B
$ git pull ssh://host/… B
$ # pull branch C
$ git pull ssh://host/… C