Fix compilation in MinGW

src/index.c

@@ -706,7 +706,7 @@ static int read_unmerged(git_index *index, const char *buffer, size_t size)
 			long tmp;
 
 			if (git__strtol32(&tmp, buffer, &endptr, 8) < GIT_SUCCESS ||
-				!endptr || endptr == buffer || *endptr || tmp > UINT_MAX)
+				!endptr || endptr == buffer || *endptr || (unsigned)tmp > UINT_MAX)
 				return GIT_ERROR;
 
 			lost->mode[i] = tmp;

src/win32/posix.c

@@ -236,16 +236,13 @@ extern int p_creat(const char *path, int mode);
 
 int p_mkstemp(char *tmp_path)
 {
-	int r;
-
 #if defined(_MSC_VER)
-	r = _mktemp_s(tmp_path, GIT_PATH_MAX);
+	if (_mktemp_s(tmp_path, GIT_PATH_MAX) != 0)
+		return GIT_EOSERR;
 #else
-	r = _mktemp(tmp_path);
-#endif
-
-	if (r != 0)
+	if (_mktemp(tmp_path) == NULL)
 		return GIT_EOSERR;
+#endif
 
 	return p_creat(tmp_path, 0744);
 }