Git plugin 4.0.0 intentionally shows the entire first line of the commit message in the "changes" page, even if that first line is very long. A global compatibility option was included to allow users to revert to the git plugin 3 behavior of truncating the first line message in the "changes" page. Unfortunately, no online help was provided for that new global configuration option.
Needs the addition of an HTML help file to match the global configuration option that was added. Text can be taken from the README.adoc description of "Show entire commit summary in changes" and placed into src/main/resources/hudson/plugins/git/GitSCM/help-showEntireCommitSummaryInChanges.html