This document discusses alternatives to using branches in software version control systems when developing software. It describes techniques like feature branching, branch by abstraction, toggles/flags, and continuous deployment that allow features to be added and tested independently without long-lived branches. The key advantages are decoupling code deployment from features and allowing A/B testing or phased feature rollout without rolling back releases. Complexity must be managed as techniques are adopted.

1. Branches
are
for
trees.
How
to
develop
so4ware
without
them.
Chris
Bushell.
September
2010.

2. Feature
branching
Merge
Commit
F1
Release
F2
F3

3. What’s
the
problem?

4. Trunk
development
Commit
Release

5. Breaking
changes

6. Branch
by
abstracIon
1
–
Introduce
an
abstracIon
over
area
of
the
system
you
want
to
change
2
–
Update
all
code
to
rely
on
the
abstracIon
3
–
Make
a
new
implementaIon
of
the
abstracIon
4
–
Remove
the
old
implementaIon
5
–
Remove
the
abstracIon
if
it’s
inelegant

7. Cherry
picking

8. Toggles/flippers/flags/bits

9. Advantages
•
Decouples
code
deployment
from
feature
•
No
need
to
roll
back
a
release,
just
disable
problemaIc
feature
•
A/B
tesIng
•
Private
betas
e.g.
turn
on
a
feature
for
5%
of
users
•
Dark
launches
•
ConInuous
deployment/delivery

10. Things
to
keep
in
mind…..
•
Complexity
and
overhead
explosion
if
toggles
aren’t
acIvely
decommissioned
•
Don’t
overload
toggles
e.g.
enItlements
(totally
different
life
spans)
•
Just
because
a
feature
is
dormant
doesn’t
mean
quality
is
not
as
important
•
Avoid
coupling
features
e.g.
feature
b
can
only
be
enabled
if
feature
a
is
enabled

11. Conclusion
•
Branching
in
VCS
isn’t
bad
•
Long
lived
branches
in
VCS
are
bad
•
Working
in
isolaIon
for
prolonged
periods
of
Ime
is
bad
•
There’s
always
another
way,
it
just
might
require
some
careful
thought
and
design

12. References
•
hap://marInfowler.com/bliki/FeatureBranch.html
•
hap://paulhammant.com/blog/branch_by_abstracIon.html
•
hap://www.se-­‐radio.net/2008/09/episode-­‐109-­‐ebays-­‐architecture-­‐principles-­‐with-­‐
randy-­‐shoup/
•
hap://velocityconference.blip.tv/file/2284377
(Flickr,
10+
releases
per
day)
•
hap://www.infoq.com/presentaIons/Feature-­‐Bits
•
ImplemenIng
Lean
So4ware
Development:
From
Concept
To
Cash,
Mary
Poppendieck,
Tom
Poppendieck