How about this.
--- read-cache.c.000	2006-05-09 15:27:56.000000000 +0000

+++ read-cache.c	2006-05-09 15:28:10.000000000 +0000

@@ -552,7 +552,7 @@
 	active_nr = ntohl(hdr->hdr_entries);

 	active_alloc = alloc_nr(active_nr);

-	active_cache = calloc(active_alloc, sizeof(struct cache_entry *));

+	active_cache = xcalloc(active_alloc, sizeof(struct cache_entry *));
 	offset = sizeof(*hdr);

 	for (i = 0; i < active_nr; i++) {
-

Looks good, thanks.  If you needed some MUA trick that other

people might benefit from please feel free to send a patch to

Documentation/SubmittingPatches "MUA specific hints" section.
Except "Subject: [PATCH] blah", commit log message (in this case

what you would have on the Subject line is to the point and you

would not need any extra log message), "Signed-off-by: whom",

and perhaps "---\n".  Material that you do not want to have in

the final commit message, like "How about this" and diffstat if

you have one, would come after the "---\n" line.
Your message formatted in the preferred way becomes like this:
	Subject: [PATCH] read-cache.c: use xcalloc() not calloc()
	Elsewhere we use xcalloc(); we should consistently do so.
        Signed-off-by: Yakov Lerner <iler.ml@gmail.com>

	---
        * How about this?
         read-cache.c |    2 +-

         1 files changed, 1 insertions(+), 1 deletions(-)
        --- read-cache.c.000	2006-05-09 15:27:56.000000000 +0000

        +++ read-cache.c	2006-05-09 15:28:10.000000000 +0000

        @@ -552,7 +552,7 @@
                active_nr = ntohl(hdr->hdr_entries);

	...
-