git: decode node IDs back into Python strings (issue6349)

db.text_factory = bytes, so the database contains only strings. The object IDs
we get from pygit2 are Python strings. b'foo' != 'foo'

This change allows the "don't reindex" optimization to work by allowing the
"cur_cache_heads == cache_heads" comparison a few lines down to succeed.

Differential Revision: https://phab.mercurial-scm.org/D8622

hgext/git/index.py

@@ -245,7 +245,10 b' def _index_repo(gitrepo, db, progress_fa'
     # TODO: we should figure out how to incrementally index history
     # (preferably by detecting rewinds!) so that we don't have to do a
     # full changelog walk every time a new commit is created.
-    cache_heads = {x[0] for x in db.execute('SELECT node FROM possible_heads')}
+    cache_heads = {
+        pycompat.sysstr(x[0])
+        for x in db.execute('SELECT node FROM possible_heads')
+    }
     walker = None
     cur_cache_heads = {h.hex for h in possible_heads}
     if cur_cache_heads == cache_heads: