Signed-off-by: Michael Haggerty <mhag...@alum.mit.edu>
---
 refs.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/refs.c b/refs.c
index 44cc2fc..efad658 100644
--- a/refs.c
+++ b/refs.c
@@ -528,6 +528,15 @@ static void sort_ref_dir(struct ref_dir *dir)
 /* Include broken references in a do_for_each_ref*() iteration: */
 #define DO_FOR_EACH_INCLUDE_BROKEN 0x01
 
+/*
+ * current_ref is a performance hack: when iterating over references
+ * using the for_each_ref*() functions, current_ref is set to the
+ * current reference's entry before calling the callback function.  If
+ * the callback function calls peel_ref(), then peel_ref() first
+ * checks whether the reference to be peeled is the current reference
+ * (it usually is) and if so, returns that reference's peeled version
+ * if it is available.  This avoids a refname lookup in a common case.
+ */
 static struct ref_entry *current_ref;
 
 /*
-- 
1.8.2.1

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