oeqa.utils.metadata: fix retrieval of git branch and revision

Always return a valid branch name, or, '(nobranch)' if the current HEAD
is detached. Also, always return the hash of the commit object that HEAD
is pointing to. Previous code returned an incorrect branch name (or
crashed) e.g. in the case of detached HEAD.

[YOCTO #10590]

(From OE-Core rev: 02d3ba17a8090bd088beb973980651d664f713bb)

Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/lib/oeqa/utils/metadata.py

@@ -72,11 +72,13 @@ def get_layers(layers):
         layer_dict[layer_name] = OrderedDict()
         try:
             repo = Repo(layer, search_parent_directories=True)
-            revision, branch = repo.head.object.name_rev.split()
         except (InvalidGitRepositoryError, NoSuchPathError):
             continue
-        layer_dict[layer_name]['branch'] = branch
-        layer_dict[layer_name]['revision'] = revision
+        layer_dict[layer_name]['revision'] = repo.head.commit.hexsha
+        try:
+            layer_dict[layer_name]['branch'] = repo.active_branch.name
+        except TypeError:
+            layer_dict[layer_name]['branch'] = '(nobranch)'
     return layer_dict
 
 def write_metadata_file(file_path, metadata):