close file on error in read_mmfile()

Reported in http://qa.debian.org/daca/cppcheck/sid/git_1.7.2.3-2.2.html
and in http://thread.gmane.org/gmane.comp.version-control.git/123042.

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

xdiff-interface.c

@@ -211,8 +211,10 @@ int read_mmfile(mmfile_t *ptr, const char *filename)
 		return error("Could not open %s", filename);
 	sz = xsize_t(st.st_size);
 	ptr->ptr = xmalloc(sz ? sz : 1);
-	if (sz && fread(ptr->ptr, sz, 1, f) != 1)
+	if (sz && fread(ptr->ptr, sz, 1, f) != 1) {
+		fclose(f);
 		return error("Could not read %s", filename);
+	}
 	fclose(f);
 	ptr->size = sz;
 	return 0;