Revert "Merge branch 'en/header-split-cache-h-part-3' into next"

This reverts commit 76ebce0b7a,
reversing changes made to 62e19d66fb,
in preparation for redoing the topic to make it buildable from the
source.

run-command.c

@@ -1,4 +1,4 @@
-#include "git-compat-util.h"
+#include "cache.h"
 #include "run-command.h"
 #include "environment.h"
 #include "exec-cmd.h"