#!/bin/sh
# this script prevents useless rebuilds after checking out sources from git, run
# it to omit build files regeneration, which otherwise require build tools being
# available
# see https://www.gnu.org/software/automake/manual/automake.html#CVS

# Usage: without arguments updates timestamps unconditionally
#        with at least one argument (not analyzed) checks timestamps and skips
#        updates if everything is up-to-date

# Note: this script sometimes doesn't work for out-of-tree builds, not sure
#       exactly why

next_second()
{
    echo Waiting for time change...
    sleep 1
}

update()
{
    echo "Updating $@"
    touch "$@"
}

# checks whether timestamps are OK, OK looks like this:
# configure.ac
#    < aclocal.m4
#        < configure build-aux/config.h.in `find . -name Makefile.in -print`
everything_is_up_to_date()
{
    if [ ! configure.ac -ot aclocal.m4 ]; then
        echo 'configure.ac is not older than aclocal.m4'
        return 1
    fi

    for file in configure build-aux/config.h.in \
               `find . -name Makefile.in -print`; do
        if [ ! aclocal.m4 -ot "$file" ]; then
            echo "aclocal.m4 is not older than $file"
            return 1
        fi
    done

    return 0
}

if [ $# -gt 0 ]; then
    if everything_is_up_to_date; then
        exit 0
    fi
fi

next_second

# aclocal-generated aclocal.m4 depends on locally-installed '.m4' macro files,
# as well as on 'configure.ac'
update aclocal.m4

next_second

# autoconf-generated configure depends on aclocal.m4 and on configure.ac
update configure

# so does autoheader-generated config.h.in
update build-aux/config.h.in

# and all the automake-generated Makefile.in files
update `find . -name Makefile.in -print`

# generated tags.c file should be newer than tags in data/vim/doc/app/
update src/tags.c