Not sure if this affects production systems, or indeed why it is not reported by everyone, but anyway I was unable to make AbstractGitSCMSource.retrieve(SCMHeadObserver, TaskListener) work in a test without this fix. (And there was no test for it.) Doing so failed with:
hudson.plugins.git.GitException: Could not init $JENKINS_HOME/caches/git-4ab...
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl$5.execute(CliGitAPIImpl.java:656)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.init(CliGitAPIImpl.java:181)
at hudson.plugins.git.GitAPI.init(GitAPI.java:217)
at jenkins.plugins.git.AbstractGitSCMSource.retrieve(AbstractGitSCMSource.java:275)
at jenkins.scm.api.SCMSource.fetch(SCMSource.java:147)
at jenkins.scm.api.SCMSource.retrieve(SCMSource.java:231)
at jenkins.scm.api.SCMSource.fetch(SCMSource.java:176)
at jenkins.plugins.git.AbstractGitSCMSourceTest.retrieveHeads(AbstractGitSCMSourceTest.java:74)
at ...
Caused by: hudson.plugins.git.GitException: Error performing command: git init $JENKINS_HOME/caches/git-4ab...
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1726)
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$5.execute(CliGitAPIImpl.java:654)
... 34 more
Caused by: java.io.IOException: Cannot run program "git" (in directory "$JENKINS_HOME/caches/git-4ab..."): error=2, No such file or directory
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1048)
at hudson.Proc$LocalProc.<init>(Proc.java:244)
at hudson.Proc$LocalProc.<init>(Proc.java:216)
at hudson.Launcher$LocalLauncher.launch(Launcher.java:803)
at hudson.Launcher$ProcStarter.start(Launcher.java:381)
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1715)
... 38 more
Caused by: java.io.IOException: error=2, No such file or directory
at java.lang.UNIXProcess.forkAndExec(Native Method)
at java.lang.UNIXProcess.<init>(UNIXProcess.java:248)
at java.lang.ProcessImpl.start(ProcessImpl.java:134)
at java.lang.ProcessBuilder.start(ProcessBuilder.java:1029)
... 43 more
Perhaps some, but not all, versions of git-client barf if you try to run git init in a nonexistent directory?
Bug
Minor