We have a job based on polling git-lab. Something went wrong in one day and it has left a .git/config.lock file in the workspace.

From that moment on, all git polling were happening but errored with the config file issue:

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FATAL: hudson.plugins.git.GitException: Failed to fetch from git@xxx.git

FATAL: hudson.plugins.git.GitException: Failed to fetch from git@xxx.git

Also:   hudson.remoting.Channel$CallSiteStackTrace: Remote call to XXX at hudson.remoting.Channel.attachCallSiteStackTrace(Channel.java:1788) at hudson.remoting.UserRequest$ExceptionResponse.retrieve(UserRequest.java:356) at hudson.remoting.Channel.call(Channel.java:998) at hudson.remoting.RemoteInvocationHandler.invoke(RemoteInvocationHandler.java:285) at com.sun.proxy.$Proxy77.setRemoteUrl(Unknown Source) at org.jenkinsci.plugins.gitclient.RemoteGitImpl.setRemoteUrl(RemoteGitImpl.java:299) at hudson.plugins.git.GitSCM.fetchFrom(GitSCM.java:897) at hudson.plugins.git.GitSCM.compareRemoteRevisionWithImpl(GitSCM.java:787) at hudson.plugins.git.GitSCM.compareRemoteRevisionWith(GitSCM.java:670) at hudson.scm.SCM.compareRemoteRevisionWith(SCM.java:401) at hudson.scm.SCM.poll(SCM.java:418) at hudson.model.AbstractProject.pollWithWorkspace(AbstractProject.java:1410) at hudson.model.AbstractProject._poll(AbstractProject.java:1380) at hudson.model.AbstractProject.poll(AbstractProject.java:1291) at hudson.triggers.SCMTrigger$Runner.runPolling(SCMTrigger.java:605) at hudson.triggers.SCMTrigger$Runner.run(SCMTrigger.java:651) at hudson.util.SequentialExecutionQueue$QueueEntry.run(SequentialExecutionQueue.java:119) at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base/java.lang.Thread.run(Thread.java:834)hudson.plugins.git.GitException: Command "git config remote.origin.url git@xxx.git" returned status code 255:stdout:stderr: error: could not lock config file .git/config: File exists
at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:2430) at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:2360) at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:2356) at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommand(CliGitAPIImpl.java:1916) at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommand(CliGitAPIImpl.java:1928) at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.setRemoteUrl(CliGitAPIImpl.java:1542) at hudson.plugins.git.GitAPI.setRemoteUrl(GitAPI.java:160) at jdk.internal.reflect.GeneratedMethodAccessor25.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at hudson.remoting.RemoteInvocationHandler$RPCRequest.perform(RemoteInvocationHandler.java:931) at hudson.remoting.RemoteInvocationHandler$RPCRequest.call(RemoteInvocationHandler.java:905) at hudson.remoting.RemoteInvocationHandler$RPCRequest.call(RemoteInvocationHandler.java:857) at hudson.remoting.UserRequest.perform(UserRequest.java:211) at hudson.remoting.UserRequest.perform(UserRequest.java:54) at hudson.remoting.Request$2.run(Request.java:369) at hudson.remoting.InterceptingExecutorService$1.call(InterceptingExecutorService.java:72) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base/java.lang.Thread.run(Thread.java:834)Caused: hudson.plugins.git.GitException: Failed to fetch from git@xxx.git at hudson.plugins.git.GitSCM.fetchFrom(GitSCM.java:909) at hudson.plugins.git.GitSCM.compareRemoteRevisionWithImpl(GitSCM.java:787) at hudson.plugins.git.GitSCM.compareRemoteRevisionWith(GitSCM.java:670)Caused: java.io.IOException at hudson.plugins.git.GitSCM.compareRemoteRevisionWith(GitSCM.java:672) at hudson.scm.SCM.compareRemoteRevisionWith(SCM.java:401) at hudson.scm.SCM.poll(SCM.java:418) at hudson.model.AbstractProject.pollWithWorkspace(AbstractProject.java:1410) at hudson.model.AbstractProject._poll(AbstractProject.java:1380) at hudson.model.AbstractProject.poll(AbstractProject.java:1291) at hudson.triggers.SCMTrigger$Runner.runPolling(SCMTrigger.java:605) at hudson.triggers.SCMTrigger$Runner.run(SCMTrigger.java:651) at hudson.util.SequentialExecutionQueue$QueueEntry.run(SequentialExecutionQueue.java:119) at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515) at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264) at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128) at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628) at java.base/java.lang.Thread.run(Thread.java:834)

Done. Took 70 ms

No changes

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Please note that the final conclusion: "No changes"

This is not the desired outcome as the polling error should have been notified, maybe by the methods defined in the job configuration.

Possible Solution (based on GitHub Webhooks Warning)

When alerts on failure of background tasks is implemented in the git plugin, it could be done through a similar user interface technique as is used by GitHub webhooks. A number appears in the top right of the Jenkins interface. When that number is clicked, a dialog appears that includes a "View" button that would open a page that lists all the problems of that type. The "Dismiss" button would clear the contents of the page that lists all the problems of that type.