CVS-like Working Practice

Mercurial allows multiple working practices. In a CVS-like world, you will typically have one central repository; let's call it the "main line". This corresponds to CVS's notion of the "trunk".

Repositories tend to be long-lived, and the "authoritative branches" are clones of the central repository.

Workflow

Developers have direct SSH access (whether that is through "normal" SSH access with each developer having their own login, or through shared SSH logins) to the central repositories on a server, and push their changes directly from their local clones into the appropriate repositories. Thus, the usual CVS practice would be as follows:

# Check for work done...
cvs update
# Do work, consider changes...
cvs diff
# Commit changes...
cvs commit

This doesn't always work out, and so the following workflow is typically required if cvs commit complains:

# Rectify conflicts, then...
cvs update
# Edit conflicts, then commit...
cvs commit

The basic workflow in Mercurial

The corresponding practice would be as follows with Mercurial:

# Check for work done (part of the update operation in CVS)...
hg pull
# Start working with the latest changes (part of the update operation in CVS)...
hg update
# Do work, consider changes...
hg diff
# Commit changes (part of the commit operation in CVS)...
hg commit
# Push changes (part of the commit operation in CVS)...
hg push

The single command equivalent of cvs update is really...

hg pull -u

Conflicts and merging in Mercurial

When pushing, hg push may complain about multiple heads being created which means that the content of the repository has been edited in different ways and has not been reconciled. Multiple heads can exist in the remote repository, but this leaves any work for reconciling the competing changes for later, which may not be desirable.

To reconcile competing changes, the following workflow becomes necessary:

# Get the remote changes and merge them...
hg pull
hg merge
# Edit any conflicts, then commit...
hg commit
# Push merged changes...
hg push

Again, you can defer pushing changes until later. The principal advantage of Mercurial here is that you do not need to be confronted with merging others' changes on every commit.

Working independently

With CVS it is not possible to perform various version control operations without getting the remote repository involved, but with Mercurial you can keep working and versioning your own work without needing to pay any attention to what others might be doing.

If you perform an hg pull but not an hg update you can check what other people have been doing, but your own work will not be affected by their changes.

Ultimately you are likely to want to combine your own work with theirs, so an update will need to happen at some stage.

If you do not perform an hg push after committing changes, you remain free to keep committing as many changesets as you like without being affected by people working elsewhere.

Branches and merging

Someone may be responsible for "backporting" changes from a branch to the main line. They do this by pulling changes from the branch and the main line into a local repository, merging appropriately, then pushing back to the main line.

When the main line reaches a release point, someone creates a clone on the server at the appropriate revision, and people who need to work on that branch clone it, then start pushing their changes back.