[JENKINS-32712] Job with Git polling "succeeds" with "no changes" although the Git polling failed

Reproduction:

• Take a working job with Git SCM Polling enabled (with the fast / "ls-remote" method)
• Provoke an error in the origin response (e.g. see Log below)
• Git Polling ends with "No changes"
• The Job stays at "blue" (successful) although the Polling clearly had errors --> the not working job might stay undiscovered quite long

Git Polling Log:

Started on Jan 31, 2016 10:00:00 PM
Using strategy: Default
[poll] Last Built Revision: Revision 1231223345345345345345345345345345345543 (refs/remotes/origin/master)
using GIT_SSH to set credentials SSH Key for someUser
 > git --version # timeout=10
 > git -c core.askpass=true ls-remote -h ssh://someUser@​localhost/example-projects/example1 # timeout=10
FATAL: hudson.plugins.git.GitException: Command "git -c core.askpass=true ls-remote -h ssh://someUser@​localhost/example-projects/example1" returned status code 128:
stdout: 
stderr: fatal: Project not found: example-projects/example1
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

hudson.util.IOException2: hudson.plugins.git.GitException: Command "git -c core.askpass=true ls-remote -h ssh://someUser@​localhost/example-projects/example1" returned status code 128:
stdout: 
stderr: fatal: Project not found: example-projects/example1
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

	at hudson.plugins.git.GitSCM.compareRemoteRevisionWith(GitSCM.java:529)
	at hudson.scm.SCM.compareRemoteRevisionWith(SCM.java:381)
	at hudson.scm.SCM.poll(SCM.java:398)
	at hudson.model.AbstractProject._poll(AbstractProject.java:1452)
	at hudson.model.AbstractProject.poll(AbstractProject.java:1355)
	at hudson.triggers.SCMTrigger$Runner.runPolling(SCMTrigger.java:510)
	at hudson.triggers.SCMTrigger$Runner.run(SCMTrigger.java:539)
	at hudson.util.SequentialExecutionQueue$QueueEntry.run(SequentialExecutionQueue.java:118)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
	at java.util.concurrent.FutureTask.run(FutureTask.java:262)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:745)
Caused by: hudson.plugins.git.GitException: Command "git -c core.askpass=true ls-remote -h ssh://someUser@​localhost/example-projects/example1" returned status code 128:
stdout: 
stderr: fatal: Project not found: example-projects/example1
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1693)
	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandWithCredentials(CliGitAPIImpl.java:1441)
	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandWithCredentials(CliGitAPIImpl.java:1335)
	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandWithCredentials(CliGitAPIImpl.java:1326)
	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.getHeadRev(CliGitAPIImpl.java:2435)
	at hudson.plugins.git.GitSCM.compareRemoteRevisionWithImpl(GitSCM.java:583)
	at hudson.plugins.git.GitSCM.compareRemoteRevisionWith(GitSCM.java:527)
	... 12 more
Done. Took 0.42 sec
No changes

Reproduction:

	
Take a working job with Git SCM Polling enabled (with the fast / "ls-remote" method)
	
Provoke an error in the origin response (e.g. see Log below)
	
Git Polling ends with "No changes"
	
 The Job stays at "blue" (successful) although the Polling clearly had errors --> the not working job might stay undiscovered quite long



Git Polling Log:

Started on Jan 31, 2016 10:00:00 PM
Using strategy: Default
[poll] Last Built Revision: Revision 1231223345345345345345345345345345345543 (refs/remotes/origin/master)
using GIT_SSH to set credentials SSH Key for someUser
 > git --version # timeout=10
 > git -c core.askpass=true ls-remote -h ssh://someUser@localhost/example-projects/example1 # timeout=10
FATAL: hudson.plugins.git.GitException: Command "git -c core.askpass=true ls-remote -h ssh://someUser@localhost/example-projects/example1" returned status code 128:
stdout: 
stderr: fatal: Project not found: example-projects/example1
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

hudson.util.IOException2: hudson.plugins.git.GitException: Command "git -c core.askpass=true ls-remote -h ssh://someUser@localhost/example-projects/example1" returned status code 128:
stdout: 
stderr: fatal: Project not found: example-projects/example1
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

	at hudson.plugins.git.GitSCM.compareRemoteRevisionWith(GitSCM.java:529)
	at hudson.scm.SCM.compareRemoteRevisionWith(SCM.java:381)
	at hudson.scm.SCM.poll(SCM.java:398)
	at hudson.model.AbstractProject._poll(AbstractProject.java:1452)
	at hudson.model.AbstractProject.poll(AbstractProject.java:1355)
	at hudson.triggers.SCMTrigger$Runner.runPolling(SCMTrigger.java:510)
	at hudson.triggers.SCMTrigger$Runner.run(SCMTrigger.java:539)
	at hudson.util.SequentialExecutionQueue$QueueEntry.run(SequentialExecutionQueue.java:118)
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
	at java.util.concurrent.FutureTask.run(FutureTask.java:262)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
	at java.lang.Thread.run(Thread.java:745)
Caused by: hudson.plugins.git.GitException: Command "git -c core.askpass=true ls-remote -h ssh://someUser@localhost/example-projects/example1" returned status code 128:
stdout: 
stderr: fatal: Project not found: example-projects/example1
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandIn(CliGitAPIImpl.java:1693)
	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandWithCredentials(CliGitAPIImpl.java:1441)
	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandWithCredentials(CliGitAPIImpl.java:1335)
	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.launchCommandWithCredentials(CliGitAPIImpl.java:1326)
	at org.jenkinsci.plugins.gitclient.CliGitAPIImpl.getHeadRev(CliGitAPIImpl.java:2435)
	at hudson.plugins.git.GitSCM.compareRemoteRevisionWithImpl(GitSCM.java:583)
	at hudson.plugins.git.GitSCM.compareRemoteRevisionWith(GitSCM.java:527)
	... 12 more
Done. Took 0.42 sec
No changes

Jenkins ver. 1.625.2<br/>
Git Plugin 2.4.1<br/>
Gerrit repository on the origin side with SSH authentification

Start at GitSCM.compareRemoteRevisionWith and follow the polling path through SCM.poll, then inspect CliGitAPIImpl.getHeadRev and the shown exception flow. Reproduce the failed ls-remote case and trace why polling ends with “No changes”; done means the failure is reported as a polling error rather than a successful no-change result, with regression coverage for the behavior.