tree acb9de58e85d3c5b9880c3c20c1427abac50fd2c
parent fbbb2969d93aef88173e0f0f59b77bd8b9f3d49d
author Xing Huang <xingkhuang@google.com> 1769461683 -0600
committer Xing Huang <xingkhuang@google.com> 1769463819 -0600

LogServlet: Handle HEAD symref to non-existent branch

The ObjectId of a Ref can be null. If HEAD is a symbolic ref to a
non-existent branch, headRef.getObjectId() will return null. The
current LogServlet code does not handle this, causing
NullPointerException in RevWalk.

This issue is particularly common when a repo is created but nothing is
pushed yet; so a HEAD symmetry is created to point to refs/heads/main by default but lacks a commit SHA.

Treat a HEAD ref with a null ObjectId as if the ref itself were null,
returning no view instead of throwing an internal error.

Change-Id: I4fe85010db0694403770923fcdf957854e72cd34
Signed-off-by: Xing Huang <xingkhuang@google.com>