[PATCH 2/7] worktree: implement worktree_prune_reason() wrapper

[Rafael Silva <rafaeloliveira.cs@gmail.com>]

The should_prune_worktree() machinery is used by the "prune" command to
identify whether a worktree is a candidate for pruning. This function
however, is not prepared to work directly with "struct worktree" and
refactoring is required not only on the function itself, but also also
changing get_worktrees() to return non-valid worktrees and address the
changes in all "worktree" sub commands.

Instead let's implement worktree_prune_reason() that accepts
"struct worktree" and uses should_prune_worktree() and returns whether
the given worktree is a candidate for pruning. As the "list" sub command
already uses a list of "struct worktree", this allow to simply check if
the working tree prunable by passing the structure directly without the
others parameters.

Also, let's add prune_reason field to the worktree structure that will
store the reason why the worktree can be pruned that is returned by
should_prune_worktree() when such reason is available.

Signed-off-by: Rafael Silva <rafaeloliveira.cs@gmail.com>
---
 worktree.c | 19 +++++++++++++++++++
 worktree.h |  7 +++++++
 2 files changed, 26 insertions(+)

diff --git a/worktree.c b/worktree.c
index 5764b0dc7c..ee14db3ab5 100644
--- a/worktree.c
+++ b/worktree.c
@@ -15,6 +15,7 @@ void free_worktrees(struct worktree **worktrees)
 		free(worktrees[i]->id);
 		free(worktrees[i]->head_ref);
 		free(worktrees[i]->lock_reason);
+		free(worktrees[i]->prune_reason);
 		free(worktrees[i]);
 	}
 	free (worktrees);
@@ -245,6 +246,24 @@ const char *worktree_lock_reason(struct worktree *wt)
 	return wt->lock_reason;
 }
 
+const char *worktree_prune_reason(struct worktree *wt, timestamp_t expire)
+{
+	if (!is_main_worktree(wt)) {
+		char *path;
+		struct strbuf reason = STRBUF_INIT;
+
+		if (should_prune_worktree(wt->id, &reason, &path, expire))
+			wt->prune_reason = strbuf_detach(&reason, NULL);
+		else
+			wt->prune_reason = NULL;
+
+		free(path);
+		strbuf_release(&reason);
+	}
+
+	return wt->prune_reason;
+}
+
 /* convenient wrapper to deal with NULL strbuf */
 static void strbuf_addf_gently(struct strbuf *buf, const char *fmt, ...)
 {
diff --git a/worktree.h b/worktree.h
index e5f4320725..24ded0f3c6 100644
--- a/worktree.h
+++ b/worktree.h
@@ -11,6 +11,7 @@ struct worktree {
 	char *id;
 	char *head_ref;		/* NULL if HEAD is broken or detached */
 	char *lock_reason;	/* private - use worktree_lock_reason */
+	char *prune_reason;     /* private - use worktree_prune_reason */
 	struct object_id head_oid;
 	int is_detached;
 	int is_bare;
@@ -73,6 +74,12 @@ int is_main_worktree(const struct worktree *wt);
  */
 const char *worktree_lock_reason(struct worktree *wt);
 
+/*
+ * Return the reason string if the given worktree should be pruned
+ * or NULL otherwise.
+ */
+const char *worktree_prune_reason(struct worktree *wt, timestamp_t expire);
+
 /*
  * Return true if worktree entry should be pruned, along with the reason for
  * pruning. Otherwise, return false and the worktree's path, or NULL if it
-- 
2.30.0.391.g469bf2a980