Microbranching, better known as "using topic branches", is a technique that I use when I wish to develop a specific, small feature without distrupting the main line of development or degrading its stability. It is also commonly used when submitting patches to an "upstream" project which you do not control; you group together a logical set of changes on a "topic branch" where they can be easily managed (revised, or kept up to date using rebasing) and then submitted as a patch series (see "Creating and submitting a patch via email with Git").

The technique consists of creating a local-only branch using a branch-savvy version control system such as Git or SVK, working on the feature, and then using git merge, svk push or similar to propagate the changes back to the trunk, or publishing them upstream as a patch series sent via email (for projects which you don’t control directly). These topic branches or microbranches are short-lived.

An example using SVK

This is an example of a creating a microbranch for the purposes of adding the #include directive to Walrus. This feature is well-suited to a microbranch because it is a relatively complicated directive (it requires a sub-parser to be spawned for each included file) but it is still reasonable to implement it within a short time frame (no more than a few days).

Creating the branch

# use the "-p" switch to create "//local/Walrus/" if needed
svk cp -p //mirrors/Walrus/trunk //local/Walrus/include-directive \
       -m "Microbranch for implementing '#include' directive"

# check out a working copy of the microbranch
svk co //local/Walrus/include-directive include-directive

# make sure all specs pass
cd include-directive
rake make
rake spec

Pulling changes in from the trunk

It’s unlikely that any changes will be made on the trunk while working on this feature because this will be such a short-lived branch.

svk pull

Pushing back changes

svk push --verbatim

The --verbatim switch prevents SVK from including SVK-specific meta-information (such as local revision numbers) in the log entries.

Disposing of the microbranch

svk co --detach
cd ..
rm -r include-directive

Updating existing copies of the trunk

Assuming there is a checked-out copy of the trunk in src:

cd src
svk up -s

And again ensuring that all specs pass:

rake spec

See also