Fix environment detection for Semaphore CI

We use semaphore CI with several parallel job and it looks like the environment isn't detected properly currently:

- I couldn't find an environment variable giving the pull request number, (supposed to come from `PULL_REQUEST_NUMBER`), however I noted `SEMAPHORE_BRANCH_ID` which is the same ID between builds pushed to the same branch. Example value: 3385909.
- The `SEMAPHORE_BUILD_NUMBER` is the same across all workers for a given push, and changes at each push. It sounds like it should be used as `number`, not as `job`. This starts at 1 on each branch, and increase on each push.
- The job ID can be obtained via `SEMAPHORE_CURRENT_JOB`, and for a given build, each worker will have their own (e.g. 1, 2, 3, etc...). Looking at the config from the other CIs, I think it should be returned as `job`.

coveralls/api.py

@@ -118,9 +118,10 @@ def load_config_from_travis():
 
     @staticmethod
     def load_config_from_semaphore():
-        job = os.environ.get('SEMAPHORE_BUILD_NUMBER')
-        pr = os.environ.get('PULL_REQUEST_NUMBER')
-        return 'semaphore-ci', job, None, pr
+        job = os.environ.get('SEMAPHORE_CURRENT_JOB')
+        number = os.environ.get('SEMAPHORE_BUILD_NUMBER')
+        pr = os.environ.get('SEMAPHORE_BRANCH_ID')
+        return 'semaphore-ci', job, number, pr
 
     @staticmethod
     def load_config_from_unknown():

tests/api/configuration_test.py

@@ -173,12 +173,14 @@ def test_travis_no_config(self):
     @mock.patch.dict(os.environ,
                      {'SEMAPHORE': 'True',
                       'SEMAPHORE_BUILD_NUMBER': '888',
-                      'PULL_REQUEST_NUMBER': '9999'},
+                      'SEMAPHORE_CURRENT_JOB': '1',
+                      'SEMAPHORE_BRANCH_ID': '9999'},
                      clear=True)
     def test_semaphore_no_config(self):
         cover = Coveralls(repo_token='xxx')
         assert cover.config['service_name'] == 'semaphore-ci'
-        assert cover.config['service_job_id'] == '888'
+        assert cover.config['service_job_id'] == '1'
+        assert cover.config['service_number'] == '888'
         assert cover.config['service_pull_request'] == '9999'
 
     @mock.patch.dict(os.environ, {'COVERALLS_SERVICE_NAME': 'xxx'}, clear=True)