Each new version of
jenkins.war is released by the process described here.
- Releases are made (roughly once per week) from the master branch, (which is built by Jenkins)
- There is an general expectation that master is should be stable; work in progress should be held in a separate branch and submitted as a pull request once ready
- If a hot fix is required (e.g. due to some fairly critical issue in the latest release), the fixes are made on master, then a new branch is made from the previous release tag (say, 1.600), and the fixes are cherry-picked, and a new release (1.601) is made from that branch. The following release will be made from the tip of the master branch as usual
This means there's generally a maximum of one week before a change in the master branch becomes available in a release.
Long-term Support (LTS) Release
There is another release line that lags behind in terms of new features, but provides more stability and a slower update cycle, called the LTS Release Line.
In March 2015, it was decided to make releases directly from the master branch.
Prior to this, there was an release candidate branch which would be branched from master up to a week in advance of the release. But very few people actively tested the RC builds, and this branching model made it more complicated to release a new Jenkins version on demand, e.g. if a hot fix was required.