build: reconfigure automatically if configure.ac changes

This provides a reduced but still useful sibling of the Automake's
"automatic Makefile rebuild" feature.  It's important to note that
we take care to enable the new rules only if the tree that has already
be configured with './configure', so that users relying on manual
configuration won't be negatively impacted.

Signed-off-by: Stefano Lattarini <stefano.lattarini@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Makefile b/Makefile
index 88a76a398ce74cc4cf9e2821118d15a50532552e..f4e8fac4915850c0c5bfdfcd03bbe6d417871646 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -2158,6 +2158,18 @@ configure: configure.ac GIT-VERSION-FILE
        autoconf -o $@ $<+ && \
        $(RM) $<+
 
+ifdef AUTOCONFIGURED
+config.status: configure
+       $(QUIET_GEN)if test -f config.status; then \
+         ./config.status --recheck; \
+       else \
+         ./configure; \
+       fi
+reconfigure config.mak.autogen: config.status
+       $(QUIET_GEN)./config.status
+.PHONY: reconfigure # This is a convenience target.
+endif
+
 XDIFF_OBJS += xdiff/xdiffi.o
 XDIFF_OBJS += xdiff/xprepare.o
 XDIFF_OBJS += xdiff/xutils.o

diff --git a/configure.ac b/configure.ac
index a63fe77b825e0ebe0d6bd2ea7126318af5f1493c..df7e376590b34b92bfd899d794bdd2627f3e31e7 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -148,6 +148,8 @@ AC_CONFIG_SRCDIR([git.c])
 config_file=config.mak.autogen
 config_in=config.mak.in
 
+GIT_CONF_SUBST([AUTOCONFIGURED], [YesPlease])
+
 # Directories holding "saner" versions of common or POSIX binaries.
 AC_ARG_WITH([sane-tool-path],
   [AS_HELP_STRING(