This is umpf, the Universal Magic Patch Functionator.
The term umpf is not only used for the tool itself, but also for the resulting artefacts built by this tool: An umpf is basically a git branch merged from different topic branches. It can come in different forms for different use cases, which are described below. An umpf can be fully qualified, which means that umpf has all information needed to convert it to any other form of umpf, but some forms of umpfs are not fully qualified.
A umerge is a git branch containing merges from topic branches.
Generally every merged tree can be a umerge, but umpf needs additional information to make
a merged tree a fully qualified umpf.
For this reason it is recommended to use umpf merge rather than git merge to built
a umerge.
A utag is a git tag with multiple parents.
The range origin/master..utag^1 contains a linear branch of all topic branches,
whereas origin/master..tag^n contains the (n-1)th topic branch.
A utag by definition is a fully qualified umpf, and it is the highest form
of an umpf, as it not only contains the topic branches but also a linear
branch which can be easily transformed into a useries.
A useries is a stack of patch files together with a series file. The series file is a regular series file which contains additional information for umpf, which can be used to reconstruct the corresponding umerge in git. useries are usually used in BSPs and not in the daily developers workflow.