Merge branch 'jk/misc-resolve-ref-unsafe-fixes' into maint

Some codepaths did not check for errors when asking what branch the
HEAD points at, which have been fixed.

* jk/misc-resolve-ref-unsafe-fixes:
  worktree: handle broken symrefs in find_shared_symref()
  log: handle broken HEAD in decoration check
  remote: handle broken symrefs
  test-ref-store: avoid passing NULL to printf

Author: gitster

builtin/remote.c

@@ -565,7 +565,7 @@ static int read_remote_branches(const char *refname,
 		item = string_list_append(rename->remote_branches, xstrdup(refname));
 		symref = resolve_ref_unsafe(refname, RESOLVE_REF_READING,
 					    NULL, &flag);
-		if (flag & REF_ISSYMREF)
+		if (symref && (flag & REF_ISSYMREF))
 			item->util = xstrdup(symref);
 		else
 			item->util = NULL;

log-tree.c

@@ -198,7 +198,7 @@ static const struct name_decoration *current_pointed_by_HEAD(const struct name_d
 
 	/* Now resolve and find the matching current branch */
 	branch_name = resolve_ref_unsafe("HEAD", 0, NULL, &rru_flags);
-	if (!(rru_flags & REF_ISSYMREF))
+	if (!branch_name || !(rru_flags & REF_ISSYMREF))
 		return NULL;
 
 	if (!starts_with(branch_name, "refs/"))

t/helper/test-ref-store.c

@@ -135,7 +135,7 @@ static int cmd_resolve_ref(struct ref_store *refs, const char **argv)
 
 	ref = refs_resolve_ref_unsafe(refs, refname, resolve_flags,
 				      sha1, &flags);
-	printf("%s %s 0x%x\n", sha1_to_hex(sha1), ref, flags);
+	printf("%s %s 0x%x\n", sha1_to_hex(sha1), ref ? ref : "(null)", flags);
 	return ref ? 0 : 1;
 }
 

worktree.c

@@ -327,7 +327,8 @@ const struct worktree *find_shared_symref(const char *symref,
 		refs = get_worktree_ref_store(wt);
 		symref_target = refs_resolve_ref_unsafe(refs, symref, 0,
 							NULL, &flags);
-		if ((flags & REF_ISSYMREF) && !strcmp(symref_target, target)) {
+		if ((flags & REF_ISSYMREF) &&
+		    symref_target && !strcmp(symref_target, target)) {
 			existing = wt;
 			break;
 		}