[PATCH v3 3/6] worktree.c: add is_main_worktree()

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

Main worktree _is_ different. You can lock a linked worktree but not the
main one, for example. Provide an API for checking that.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 worktree.c | 5 +++++
 worktree.h | 5 +++++
 2 files changed, 10 insertions(+)

diff --git a/worktree.c b/worktree.c
index 4dd7b77..6432eec 100644
--- a/worktree.c
+++ b/worktree.c
@@ -250,6 +250,11 @@ struct worktree *find_worktree(struct worktree **list,
 	return *list;
 }
 
+int is_main_worktree(const struct worktree *wt)
+{
+	return !wt->id;
+}
+
 int is_worktree_being_rebased(const struct worktree *wt,
 			      const char *target)
 {
diff --git a/worktree.h b/worktree.h
index 7ad15da..e1c4715 100644
--- a/worktree.h
+++ b/worktree.h
@@ -37,6 +37,11 @@ extern struct worktree *find_worktree(struct worktree **list,
 				      const char *prefix,
 				      const char *arg);
 
+/*
+ * Return true if the given worktree is the main one.
+ */
+extern int is_main_worktree(const struct worktree *wt);
+
 /*
  * Free up the memory for worktree(s)
  */
-- 
2.8.2.524.g6ff3d78