Check for branch merge requires child commit

[rcraggs]

The rule "commit-with-message-was-merged-into-branch" only works if the merge in question had a child commit made afterwards. It happens in the function here:

gitruler/src/main/java/gitruler/GitFunctions.java

Line 380 in c643f9d

boolean isChildOfCommitOnBranch(String branch, String commitMessageContents, boolean ignoreMessageCase) throws IOException, GitAPIException, BranchNotFoundException {