Move git_sort(), a stable sort, into into libgit.a

The `qsort()` function is not guaranteed to be stable, i.e. it does not
promise to maintain the order of items it is told to consider equal. In
contrast, the `git_sort()` function we carry in `compat/qsort.c` _is_
stable, by virtue of implementing a merge sort algorithm.

In preparation for using a stable sort in Git's rename detection, move
the stable sort into `libgit.a` so that it is compiled in
unconditionally, and rename it to `git_stable_qsort()`.

Note: this also makes the hack obsolete that was introduced in
fe21c6b285d (mingw: reencode environment variables on the fly (UTF-16
<-> UTF-8), 2018-10-30), where we included `compat/qsort.c` directly in
`compat/mingw.c` to use the stable sort.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/git-compat-util.h b/git-compat-util.h
index 83be89de0a..7ec2c8fe31 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -1094,10 +1094,10 @@ static inline int strtol_i(char const *s, int base, int *result)
 	return 0;
 }
 
+void git_stable_qsort(void *base, size_t nmemb, size_t size,
+		      int(*compar)(const void *, const void *));
 #ifdef INTERNAL_QSORT
-void git_qsort(void *base, size_t nmemb, size_t size,
-	       int(*compar)(const void *, const void *));
-#define qsort git_qsort
+#define qsort git_stable_qsort
 #endif
 
 #define QSORT(base, n, compar) sane_qsort((base), (n), sizeof(*(base)), compar)
@@ -1108,6 +1108,9 @@ static inline void sane_qsort(void *base, size_t nmemb, size_t size,
 		qsort(base, nmemb, size, compar);
 }
 
+#define STABLE_QSORT(base, n, compar) \
+	git_stable_qsort((base), (n), sizeof(*(base)), compar)
+
 #ifndef HAVE_ISO_QSORT_S
 int git_qsort_s(void *base, size_t nmemb, size_t size,
 		int (*compar)(const void *, const void *, void *), void *ctx);