The original GitException from a failed merge was good enough, no need to rethrow it

[jglick]

Noticed while testing jenkinsci/github-branch-source-plugin#60.

hudson.plugins.git.GitException: Could not merge AnyObjectId[99608938c2e9f12e73c4aba94b81a4dbdaffb937]
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl$3.execute(CliGitAPIImpl.java:590)
    at org.jenkinsci.plugins.github_branch_source.GitHubSCMSource$MergeWith.decorateRevisionToBuild(GitHubSCMSource.java:664)
    at hudson.plugins.git.GitSCM.determineRevisionToBuild(GitSCM.java:991)
    at hudson.plugins.git.GitSCM.checkout(GitSCM.java:1080)
    at …
Caused by: hudson.plugins.git.GitException: Command "git merge 99608938c2e9f12e73c4aba94b81a4dbdaffb937" returned status code 1:
stdout: Auto-merging Jenkinsfile
CONFLICT (content): Merge conflict in Jenkinsfile
Automatic merge failed; fix conflicts and then commit the result.

stderr: 
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1719)
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1695)
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1691)
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommand(CliGitAPIImpl.java:1321)
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl$3.execute(CliGitAPIImpl.java:588)
    ... 9 more

simplified to

hudson.plugins.git.GitException: Command "git merge 99608938c2e9f12e73c4aba94b81a4dbdaffb937" returned status code 1:
stdout: Auto-merging Jenkinsfile
CONFLICT (content): Merge conflict in Jenkinsfile
Automatic merge failed; fix conflicts and then commit the result.

stderr: 
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1715)
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1691)
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1687)
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommand(CliGitAPIImpl.java:1317)
    at org.jenkinsci.plugins.gitclient.CliGitAPIImpl$3.execute(CliGitAPIImpl.java:587)
    at org.jenkinsci.plugins.github_branch_source.GitHubSCMSource$MergeWith.decorateRevisionToBuild(GitHubSCMSource.java:664)
    at hudson.plugins.git.GitSCM.determineRevisionToBuild(GitSCM.java:991)
    at hudson.plugins.git.GitSCM.checkout(GitSCM.java:1080)
    at …

@reviewbybees

[ghost]

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[jglick]

@MarkEWaite whatever your PR builder is checking, I cannot see the result.