Enable gerrit/gitlab/github refspecs

By default git only fetches references under the refs/heads/ tree,
this patch adds support to kas to enable you to specify references
outside of the ref/heads tree.  This is useful as it allows you to
use uncommitted gerrit patchsets, Gitlab merge requests or github
pull requests that live under refs/changes/, refs/merge-requests
and refs/pull as the reference for a repo allowing the use of
in development changes.  When a refsepc is defined that starts
with refs/ an additional git fetch operation is preformed on the
repo to explicitly fetch the reference given so it can be checked
out for use.

Signed-off-by: Drew Reed <drew.reed@arm.com>
Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

tests/test_refspec.py

@@ -63,3 +63,27 @@ def test_refspec_switch(changedir, tmpdir):
                            fail=False, liveupdate=False)
     assert rc == 0
     assert output.strip() == '907816a5c4094b59a36aec12226e71c461c05b77'
+
+
+def test_refspec_absolute(changedir, tmpdir):
+    """
+        Test that the local git clone works when a absolute refspec
+        is givvn.
+    """
+    tdir = str(tmpdir.mkdir('test_refspec_absolute'))
+    shutil.rmtree(tdir, ignore_errors=True)
+    shutil.copytree('tests/test_refspec', tdir)
+    os.chdir(tdir)
+
+    kas.kas(['shell', 'test3.yml', '-c', 'true'])
+    (rc, output) = run_cmd(['git', 'symbolic-ref', '-q', 'HEAD'],
+                           cwd='kas_abs', fail=False, liveupdate=False)
+    assert rc != 0
+    assert output.strip() == ''
+    (rc, output_kas_abs) = run_cmd(['git', 'rev-parse', 'HEAD'],
+                                   cwd='kas_abs', fail=False, liveupdate=False)
+    assert rc == 0
+    (rc, output_kas_rel) = run_cmd(['git', 'rev-parse', 'HEAD'],
+                                   cwd='kas_rel', fail=False, liveupdate=False)
+    assert rc == 0
+    assert output_kas_abs.strip() == output_kas_rel.strip()

tests/test_refspec/test3.yml

@@ -0,0 +1,13 @@
+header:
+  version: 8
+
+repos:
+  this:
+
+  kas_abs:
+    url: https://github.com/siemens/kas.git
+    refspec: refs/heads/master
+
+  kas_rel:
+    url: https://github.com/siemens/kas.git
+    refspec: master