Why is preoutgoing hook executed on Strip in Mercurial?

To avoid the execution of my hook code, I've added the following lines of code to the very beginning of my hook:

if "%HG_SOURCE%" == "strip" (
    exit /b 0
)

Both outgoing and preoutgoing will be provided with a parameter indicating the source action. In Python, this parameter is called source, otherwise you can access the environment variable HG_SOURCE:

• hg push → HG_SOURCE is push
• hg strip → HG_SOURCE is strip

Based on that observation, you can simply evaluate the initial command.

Sources:

• preoutgoing
• Sources of changesets