Re: [PATCH v2] build: do not automatically reconfigure unless configure.ac changed

[Junio C Hamano <gitster@pobox.com>]

Stefano Lattarini <stefano.lattarini@gmail.com> writes:

> On 01/02/2013 09:48 AM, Jonathan Nieder wrote:
>> Jeff King wrote:
>> 
>>> It seems I am late to the party. But FWIW, this looks the most sane to
>>> me of the patches posted in this thread.
>> ...
> FYI, this seems a sane approach to me....
> The only nit I have to offer is that I'd like to see more comments in
> the git Makefile about why this "semi-hack" is needed.

Thanks, everybody.

Please eyeball the below for (hopefully) the last time, to be
eventually merged to maint-1.7.12, maint-1.8.0 and maint (aka
maint-1.8.1) branches.

-- >8 --
From: Jonathan Nieder <jrnieder@gmail.com>
Date: Wed, 2 Jan 2013 00:25:44 -0800
Subject: [PATCH] build: do not automatically reconfigure unless configure.ac changed

Starting with v1.7.12-rc0~4^2 (build: reconfigure automatically if
configure.ac changes, 2012-07-19), "config.status --recheck" is
automatically run every time the "configure" script changes.  In
particular, that means the configuration procedure repeats whenever
the version number changes (since the configure script changes to
support "./configure --version" and "./configure --help"), making
bisecting painfully slow.

The intent was to make the reconfiguration process only trigger for
changes to configure.ac's logic.  Tweak the Makefile rule to match
that intent by depending on configure.ac instead of configure.

Reported-by: Martin von Zweigbergk <martinvonz@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Jeff King <peff@peff.net>
Reviewed-by: Stefano Lattarini <stefano.lattarini@gmail.com>
---
 Makefile | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index 26b697d..2f5e2ab 100644
--- a/Makefile
+++ b/Makefile
@@ -2167,8 +2167,14 @@ configure: configure.ac GIT-VERSION-FILE
 	$(RM) $<+
 
 ifdef AUTOCONFIGURED
-config.status: configure
-	$(QUIET_GEN)if test -f config.status; then \
+# We avoid depending on 'configure' here, because it gets rebuilt
+# every time GIT-VERSION-FILE is modified, only to update the embedded
+# version number string, which config.status does not care about.  We
+# do want to recheck when the platform/environment detection logic
+# changes, hence this depends on configure.ac.
+config.status: configure.ac
+	$(QUIET_GEN)$(MAKE) configure && \
+	if test -f config.status; then \
 	  ./config.status --recheck; \
 	else \
 	  ./configure; \
-- 
1.8.1.200.gd2acdf2