Karthik Nayak [off-list ref] writes:

We cannot directly add the new syntax checks to `is_pseudoref_syntax()`
because the function is also used by `is_current_worktree_ref()` and
making it stricter to match only known pseudorefs might have unintended
consequences due to files like 'BISECT_START' which isn't a pseudoref
but sometimes contains object ID.

Well described.

Let's end an array's initializer with a trailing comma, to help
future patches to add entries to this array without unnecessary
patch noise. 

+	};
+	size_t i;
+
+	if (!is_pseudoref_syntax(refname))
+		return 0;
+
+	if (ends_with(refname, "_HEAD"))
+		return refs_ref_exists(refs, refname);
+
+	for (i = 0; i < ARRAY_SIZE(irregular_pseudorefs); i++)
+		 if (!strcmp(refname, irregular_pseudorefs[i]))
+			 return refs_ref_exists(refs, refname);
+
+	return 0;
+}

The above uses refs_ref_exists() because we want these to
successfully resolve for reading.

+int is_headref(struct ref_store *refs, const char *refname)
+{
+	if (!strcmp(refname, "HEAD"))
+		return refs_ref_exists(refs, refname);

Given that "git for-each-ref refs/remotes" does not show
"refs/remotes/origin/HEAD" in the output when we do not have the
remote-tracking branch that symref points at, we probably do want
to omit "HEAD" from the output when the HEAD symref points at an
unborn branch.  If refs_ref_exists() says "no, it does not exist"
in such a case, we are perfectly fine with this code.

We do not have to worry about the unborn state for pseudorefs
because they would never be symbolic.  But that in turn makes me
suspect that the check done with refs_ref_exists() in the
is_pseudoref() helper is a bit too lenient by allowing it to be a
symbolic ref.  Shouldn't we be using a check based on
read_ref_full(), like we did in another topic recently [*]?


[Reference]

 * https://lore.kernel.org/git/xmqqzfxa9usx.fsf@gitster.g/ (local)