add mergesort() for linked lists

This adds a generic bottom-up mergesort implementation for singly linked
lists.  It was inspired by Simon Tatham's webpage on the topic[1], but
not so much by his implementation -- for no good reason, really, just a
case of NIH.

[1] http://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/mergesort.h b/mergesort.h
new file mode 100644
index 0000000000..d6e5f4a732
--- /dev/null
+++ b/mergesort.h
@@ -0,0 +1,9 @@
+#ifndef MERGESORT_H
+#define MERGESORT_H
+
+void *mergesort(void *list,
+		void *(*get_next_fn)(const void *),
+		void (*set_next_fn)(void *, void *),
+		int (*compare_fn)(const void *, const void *));
+
+#endif