allow hooks to ignore their standard input stream

Since ec7dbd145 (receive-pack: allow hooks to ignore its
standard input stream) the pre-receive and post-receive
hooks ignore SIGPIPE. Do the same for the remaining hooks
pre-push and post-rewrite, which read from standard input.
The same arguments for ignoring SIGPIPE apply.

Include test by Jeff King which checks that SIGPIPE does not
cause pre-push hook failure. With the use of git update-ref
--stdin it is fast enough to be enabled by default.

Signed-off-by: Clemens Buchacher <clemens.buchacher@intel.com>
Signed-off-by: Jeff King <peff@peff.net>
diff --git a/builtin/commit.c b/builtin/commit.c
index dca09e2..f2a8b78 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -32,6 +32,7 @@
 #include "sequencer.h"
 #include "notes-utils.h"
 #include "mailmap.h"
+#include "sigchain.h"
 
 static const char * const builtin_commit_usage[] = {
 	N_("git commit [<options>] [--] <pathspec>..."),
@@ -1537,8 +1538,10 @@
 		return code;
 	n = snprintf(buf, sizeof(buf), "%s %s\n",
 		     sha1_to_hex(oldsha1), sha1_to_hex(newsha1));
+	sigchain_push(SIGPIPE, SIG_IGN);
 	write_in_full(proc.in, buf, n);
 	close(proc.in);
+	sigchain_pop(SIGPIPE);
 	return finish_command(&proc);
 }