worktree.c: make find_shared_symref() return struct worktree *

This gives the caller more information and they can answer things like,
"is it the main worktree" or "is it the current worktree". The latter
question is needed for the "checkout a rebase branch" case later.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

branch.c

@@ -336,13 +336,14 @@ void remove_branch_state(void)
 
 void die_if_checked_out(const char *branch)
 {
-	char *existing;
+	const struct worktree *wt;
 
-	existing = find_shared_symref("HEAD", branch);
-	if (existing) {
-		skip_prefix(branch, "refs/heads/", &branch);
-		die(_("'%s' is already checked out at '%s'"), branch, existing);
-	}
+	wt = find_shared_symref("HEAD", branch);
+	if (!wt)
+		return;
+	skip_prefix(branch, "refs/heads/", &branch);
+	die(_("'%s' is already checked out at '%s'"),
+	    branch, wt->path);
 }
 
 int replace_each_worktree_head_symref(const char *oldref, const char *newref)

builtin/branch.c

@@ -220,12 +220,12 @@ static int delete_branches(int argc, const char **argv, int force, int kinds,
 		name = mkpathdup(fmt, bname.buf);
 
 		if (kinds == FILTER_REFS_BRANCHES) {
-			char *worktree = find_shared_symref("HEAD", name);
-			if (worktree) {
+			const struct worktree *wt =
+				find_shared_symref("HEAD", name);
+			if (wt) {
 				error(_("Cannot delete branch '%s' "
 					"checked out at '%s'"),
-				      bname.buf, worktree);
-				free(worktree);
+				      bname.buf, wt->path);
 				ret = 1;
 				continue;
 			}

builtin/notes.c

@@ -847,15 +847,15 @@ static int merge(int argc, const char **argv, const char *prefix)
 		update_ref(msg.buf, default_notes_ref(), result_sha1, NULL,
 			   0, UPDATE_REFS_DIE_ON_ERR);
 	else { /* Merge has unresolved conflicts */
-		char *existing;
+		const struct worktree *wt;
 		/* Update .git/NOTES_MERGE_PARTIAL with partial merge result */
 		update_ref(msg.buf, "NOTES_MERGE_PARTIAL", result_sha1, NULL,
 			   0, UPDATE_REFS_DIE_ON_ERR);
 		/* Store ref-to-be-updated into .git/NOTES_MERGE_REF */
-		existing = find_shared_symref("NOTES_MERGE_REF", default_notes_ref());
-		if (existing)
+		wt = find_shared_symref("NOTES_MERGE_REF", default_notes_ref());
+		if (wt)
 			die(_("A notes merge into %s is already in-progress at %s"),
-			    default_notes_ref(), existing);
+			    default_notes_ref(), wt->path);
 		if (create_symref("NOTES_MERGE_REF", default_notes_ref(), NULL))
 			die("Failed to store link to current notes ref (%s)",
 			    default_notes_ref());

worktree.c

@@ -191,14 +191,19 @@ const char *get_worktree_git_dir(const struct worktree *wt)
 		return git_common_path("worktrees/%s", wt->id);
 }
 
-char *find_shared_symref(const char *symref, const char *target)
+const struct worktree *find_shared_symref(const char *symref,
+					  const char *target)
 {
-	char *existing = NULL;
+	const struct worktree *existing = NULL;
 	struct strbuf path = STRBUF_INIT;
 	struct strbuf sb = STRBUF_INIT;
-	struct worktree **worktrees = get_worktrees();
+	static struct worktree **worktrees;
 	int i = 0;
 
+	if (worktrees)
+		free_worktrees(worktrees);
+	worktrees = get_worktrees();
+
 	for (i = 0; worktrees[i]; i++) {
 		strbuf_reset(&path);
 		strbuf_reset(&sb);
@@ -211,14 +216,13 @@ char *find_shared_symref(const char *symref, const char *target)
 		}
 
 		if (!strcmp(sb.buf, target)) {
-			existing = xstrdup(worktrees[i]->path);
+			existing = worktrees[i];
 			break;
 		}
 	}
 
 	strbuf_release(&path);
 	strbuf_release(&sb);
-	free_worktrees(worktrees);
 
 	return existing;
 }

worktree.h

@@ -35,10 +35,10 @@ extern void free_worktrees(struct worktree **);
 
 /*
  * Check if a per-worktree symref points to a ref in the main worktree
- * or any linked worktree, and return the path to the exising worktree
- * if it is.  Returns NULL if there is no existing ref.  The caller is
- * responsible for freeing the returned path.
+ * or any linked worktree, and return the worktree that holds the ref,
+ * or NULL otherwise. The result may be destroyed by the next call.
  */
-extern char *find_shared_symref(const char *symref, const char *target);
+extern const struct worktree *find_shared_symref(const char *symref,
+						 const char *target);
 
 #endif