worktree.c: add is_worktree_locked()

We need this later to avoid double locking a worktree, or unlocking one
when it's not even locked.

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

Author: pclouds

worktree.c

@@ -13,6 +13,7 @@ void free_worktrees(struct worktree **worktrees)
 		free(worktrees[i]->path);
 		free(worktrees[i]->id);
 		free(worktrees[i]->head_ref);
+		free(worktrees[i]->lock_reason);
 		free(worktrees[i]);
 	}
 	free (worktrees);
@@ -98,6 +99,8 @@ static struct worktree *get_main_worktree(void)
 	worktree->is_detached = is_detached;
 	worktree->is_current = 0;
 	add_head_info(&head_ref, worktree);
+	worktree->lock_reason = NULL;
+	worktree->lock_reason_valid = 0;
 
 done:
 	strbuf_release(&path);
@@ -143,6 +146,8 @@ static struct worktree *get_linked_worktree(const char *id)
 	worktree->is_detached = is_detached;
 	worktree->is_current = 0;
 	add_head_info(&head_ref, worktree);
+	worktree->lock_reason = NULL;
+	worktree->lock_reason_valid = 0;
 
 done:
 	strbuf_release(&path);
@@ -234,6 +239,29 @@ int is_main_worktree(const struct worktree *wt)
 	return !wt->id;
 }
 
+const char *is_worktree_locked(struct worktree *wt)
+{
+	assert(!is_main_worktree(wt));
+
+	if (!wt->lock_reason_valid) {
+		struct strbuf path = STRBUF_INIT;
+
+		strbuf_addstr(&path, worktree_git_path(wt, "locked"));
+		if (file_exists(path.buf)) {
+			struct strbuf lock_reason = STRBUF_INIT;
+			if (strbuf_read_file(&lock_reason, path.buf, 0) < 0)
+				die_errno(_("failed to read '%s'"), path.buf);
+			strbuf_trim(&lock_reason);
+			wt->lock_reason = strbuf_detach(&lock_reason, NULL);
+		} else
+			wt->lock_reason = NULL;
+		wt->lock_reason_valid = 1;
+		strbuf_release(&path);
+	}
+
+	return wt->lock_reason;
+}
+
 int is_worktree_being_rebased(const struct worktree *wt,
 			      const char *target)
 {

worktree.h

@@ -5,10 +5,12 @@ struct worktree {
 	char *path;
 	char *id;
 	char *head_ref;
+	char *lock_reason;	/* internal use */
 	unsigned char head_sha1[20];
 	int is_detached;
 	int is_bare;
 	int is_current;
+	int lock_reason_valid;
 };
 
 /* Functions for acting on the information about worktrees. */
@@ -42,6 +44,12 @@ extern struct worktree *find_worktree(struct worktree **list,
  */
 extern int is_main_worktree(const struct worktree *wt);
 
+/*
+ * Return the reason string if the given worktree is locked or NULL
+ * otherwise.
+ */
+extern const char *is_worktree_locked(struct worktree *wt);
+
 /*
  * Free up the memory for worktree(s)
  */