Git Cohesion

API ID: GitCohesion
Languages: Any
Targets: Architectures

The percentage of commits that are cohesive.

A cohesive commit is a commit whose changed files are all in the same architecture. A non-cohesive commit changes files across architectures. The value for a root architecture considers each sub-architecture as a separate group. The value for a non-root architecture forms a group with all descendants and everything else is a different group. So, for this sample architecture:

• Root
  • A
    • A1
    • A2
    • AA
      • AA1
      • AA2
  • B
    • B1
    • B2

When calculating cohesion for "Root":

1. A commit touching A1 and A2 is cohesive because it only changes the sub-architecture "A".
2. A commit touching A1 and B1 is not cohesive because it changes the sub-architectures "A" and "B".
3. A commit touching A1 and AA2 is not cohesive because it changes the sub-architectures "A" and "AA".

When calculating cohesion for "A":

1. A commit touching A1 and A2 is cohesive because it only changes files within "A".
2. A commit touching A1 and B1 is not cohesive because it changes a file outside of "A" (in "B").
3. A commit touching A1 and AA2 is cohesive because it only changes files within "A".

Note the difference in the 3rd bullet point for the two scenarios. For a root architecture, each nested architecture is considered as it's own architecture. For a non-root architecture, nested architectures within the target are considered as part of the target.

See also the Git Solution, the blog article ↗ describing the Git plugins, and the related coupling plugins which work on files: the interactive report Git Coupling, and the metrics Git Average Coupling, Git Max Coupling, Git Coupled Files and Git Strongly Coupled Files .