GHE returning 404 when trying to fetch reference file for master branch

[suryatej16]

Describe the bug
Due to the change introduced in #822, GHE v2.18 will return a 404 when you attempt to access api/v3/repos/:org/:repo/git/ref/heads/master instead of api/v3/repos/:org/:repo/git/refs/heads/master. This is causing the Jenkins Github Branch Source plugin to throw the following stacktrace:

java.io.FileNotFoundException: https://xxxxxxxxx/api/v3/repos/:org/:repo/git/ref/heads/master
	at com.squareup.okhttp.internal.huc.HttpURLConnectionImpl.getInputStream(HttpURLConnectionImpl.java:243)
	at com.squareup.okhttp.internal.huc.DelegatingHttpsURLConnection.getInputStream(DelegatingHttpsURLConnection.java:210)
	at com.squareup.okhttp.internal.huc.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:25)
	at org.kohsuke.github.GitHubHttpUrlConnectionClient$HttpURLConnectionResponseInfo.bodyStream(GitHubHttpUrlConnectionClient.java:197)
	at org.kohsuke.github.GitHubResponse$ResponseInfo.getBodyAsString(GitHubResponse.java:321)
	at org.kohsuke.github.GitHubResponse.parseBody(GitHubResponse.java:85)
	at org.kohsuke.github.Requester.lambda$fetch$1(Requester.java:71)
	at org.kohsuke.github.GitHubClient.createResponse(GitHubClient.java:420)
	at org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:374)
Caused: org.kohsuke.github.GHFileNotFoundException: https://xxxxxx/api/v3/repos/:org/:repo/git/ref/heads/master {"message":"Not Found","documentation_url":"https://developer.github.com/enterprise/2.18/v3"}
	at org.kohsuke.github.GitHubClient.interpretApiError(GitHubClient.java:451)
	at org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:382)
	at org.kohsuke.github.GitHubClient.sendRequest(GitHubClient.java:326)
	at org.kohsuke.github.Requester.fetch(Requester.java:71)
	at org.kohsuke.github.GHRepository.getRef(GHRepository.java:1594)
	at org.jenkinsci.plugins.github_branch_source.GitHubSCMSource.retrieve(GitHubSCMSource.java:1602)
	at jenkins.scm.api.SCMSource.fetch(SCMSource.java:582)
	at org.jenkinsci.plugins.workflow.multibranch.SCMBinder.create(SCMBinder.java:98)
	at org.jenkinsci.plugins.workflow.job.WorkflowRun.run(WorkflowRun.java:309)
	at hudson.model.ResourceController.execute(ResourceController.java:97)
	at hudson.model.Executor.run(Executor.java:429)

To Reproduce
Steps to reproduce the behavior:

1. Run a curl -X GET https://<host>/api/v3/repos/:org/:repo/git/ref/heads/master against GHE v.2.18 and you'll get a 404 in response

Expected behavior
Should return the ref for master branch.

Desktop (please complete the following information):
Jenkins Github Branch Source plugin 2.8.0
GHE 2.18

Additional context
Add any other context about the problem here.

[suryatej16]

@bitwiseman I tried to file an issue with the Jenkins plugin (https://github.com/jenkinsci/github-branch-source-plugin) as well, but don't see the Issues tab active. I see you're a contributor there as well. Once this is fixed, could you update the plugin and release a new version?

[bitwiseman]

@suryatej16
Thanks!
Issues for Jenkins are filed on the Jenkins JIRA - issues.jenkins.io .

I'll update shortly.

[bitwiseman]

Waiting for repo's to update to publish the plugin.

[solvingj]

was very confused until i found this issue. thanks to all.