Keep a record of what HEAD points at

codearchiver/modules/git.py

@@ -18,6 +18,7 @@ class GitMetadata(codearchiver.core.Metadata):
 		codearchiver.core.MetadataField(key = 'Git version', required = True, repeatable = False),
 		codearchiver.core.MetadataField(key = 'Based on bundle', required = False, repeatable = True),
 		codearchiver.core.MetadataField(key = 'Ref', required = True, repeatable = True),
+		codearchiver.core.MetadataField(key = 'Head', required = True, repeatable = False),
 		codearchiver.core.MetadataField(key = 'Root commit', required = True, repeatable = True),
 		codearchiver.core.MetadataField(key = 'Object', required = False, repeatable = True),
 	)
@@ -75,6 +76,11 @@ class Git(codearchiver.core.Module):
 		rootCommits = list(filter(None, rootCommits.splitlines()))
 		_, objects, _ = codearchiver.subprocess.run_with_log(['git', 'cat-file', '--batch-check', '--batch-all-objects', '--unordered', '--buffer'], cwd = directory)
 		objects = {oid: otype for oid, otype, osize in map(functools.partial(str.split, sep = ' '), objects.splitlines())}
+		with open(os.path.join(directory, 'HEAD'), 'r') as fp:
+			head = fp.read()
+		if not head.startswith('ref: refs/heads/') or not head.endswith('\n'):
+			raise RuntimeError(f'Unexpected HEAD content: {head!r}')
+		head = head[:-1]  # Remove trailing \n
 
 		# Check whether there are relevant prior bundles to create an incremental one
 		commitsAndTags = {oid for oid, otype in objects.items() if otype in ('commit', 'tag')}
@@ -168,6 +174,7 @@ class Git(codearchiver.core.Module):
 			metadata.append('Based on bundle', oldBundle)
 		for line in refs:
 			metadata.append('Ref', line)
+		metadata.append('Head', head)
 		for commitId in rootCommits:
 			metadata.append('Root commit', commitId)
 		for oid, otype in indexObjects.items():