From eab6ceab6e37fb7ba088e4ec0a33d05487a23ca0 Mon Sep 17 00:00:00 2001
From: Lucio Andrés Illanes Albornoz (arab, vxp) <lucio@lucioillanes.de>
Date: Apr 01 2018 16:52:32 +0000
Subject: subr/build_checks.subr: don't build given --as-needed and no new commits to midipix_build since the last build.

etc/build.usage, subr/build_args.subr: adds --as-needed.
vars/build.vars:dist_target: adds dist_gitref.
vars/dist_gitref.vars: print git-rev-parse(1) HEAD to ${PREFIX}/build.gitref.

---

diff --git a/etc/build.usage b/etc/build.usage
index c9a0466..d5bbd50 100644
--- a/etc/build.usage
+++ b/etc/build.usage
@@ -36,6 +36,7 @@ usage: ./build.sh [-4|6] [-a nt32|nt64] [-b debug|release]
                                 default compression is xz.
         -v[v[v]]                Be verbose; -vv: always print package logs; -vvv: logs fileops.
         -x                      Set xtrace during package builds; implies -vv.
+        --as-needed             Don't build unless the midipix_build repository has received new commits.
         --debug-minipix         Don't strip(1) minipix binaries to facilitate debugging minipix.
         <target>[ ..]           One of:
                                 host or host_tools, host_toolchain_deps, host_toolchain, host_toolchain_mingw32,
diff --git a/subr/build_args.subr b/subr/build_args.subr
index 0a3390c..ea6eabf 100644
--- a/subr/build_args.subr
+++ b/subr/build_args.subr
@@ -9,6 +9,7 @@ BUILD_ARGS_SPEC="
 	BUILD:arg:-b:
 	ARG_CLEAN:-c:
 	ARG_CLEAN_BUILDS:arg:-C:
+	ARG_AS_NEEDED:--as-needed:
 	ARG_DEBUG_MINIPIX:--debug-minipix:
 	ARG_OFFLINE:-N:
 	ARG_PACKAGE:-p:
diff --git a/subr/build_checks.subr b/subr/build_checks.subr
index 055ed87..5abeab2 100644
--- a/subr/build_checks.subr
+++ b/subr/build_checks.subr
@@ -33,6 +33,12 @@ build_checks() {
 	if [ ${_exit:-0} = 1 ]; then
 		exit 1;
 	fi;
+	if [ "${ARG_AS_NEEDED:-0}" -eq 1 ]\
+	&& [ -e "${PREFIX}/build.gitref" ]\
+	&& [ "$(git rev-parse HEAD)" = "$(cat "${PREFIX}/build.gitref")" ]; then
+		ex_rtl_log_msg info "Git repository has not changed since last build and --as-needed was specified.";
+		exit 0;
+	fi;
 	if [ ${ARG_CLEAN:-0} -eq 1 ]; then
 		ex_rtl_log_msg info "-c specified, cleaning prefix...";
 		for _pname in ${DEFAULT_CLEAR_PREFIX_PATHS}; do
diff --git a/vars/build.vars b/vars/build.vars
index e64a597..2f1ad5a 100644
--- a/vars/build.vars
+++ b/vars/build.vars
@@ -1204,7 +1204,7 @@ DIST_MINIPIX_PREFIX="${PREFIX}/minipix_dist";
 # Build target dist_target
 #
 DIST_TARGET_NO_LOG_VARS=1;
-DIST_TARGET_PACKAGES="dist_minipix_dist dist_etc dist_digest dist_tarballs";
+DIST_TARGET_PACKAGES="dist_minipix_dist dist_etc dist_digest dist_gitref dist_tarballs";
 
 #
 # Build targets
diff --git a/vars/dist_gitref.vars b/vars/dist_gitref.vars
new file mode 100644
index 0000000..eff4912
--- /dev/null
+++ b/vars/dist_gitref.vars
@@ -0,0 +1,9 @@
+#
+# set -o errexit -o noglob are assumed.
+#
+
+pkg_dist_gitref_all() {
+	git -C "${MIDIPIX_BUILD_PWD}" rev-parse HEAD > "${PREFIX}/build.gitref";
+};
+
+# vim:filetype=sh