Given that this time I think I understood, that the bug was really bad
for users, I went ahead and applied it.
Tom, feel free to strengthen instdata2!
Here is what I committed.
#! /bin/sh
# Test that installing under $exec_prefix is handled by install-exec.
# Testing with headers for instance.
. $srcdir/defs || exit 1
cat >Makefile.am << 'EOF'
# User directories.
inclexecdir = $(exec_prefix)/include
inclexec_HEADERS = my-config.h
incldatadir = $(prefix)/include
incldata_HEADERS = my-data.h
## Standard directories: _DATA
## Commented out are invalid combinations.
##bin_DATA = data
##sbin_DATA = data
##libexec_DATA = data
data_DATA = data
sysconf_DATA = data
localstate_DATA = data
##lib_DATA = data
##info_DATA = data
##man_DATA = data
##include_DATA = data
##oldinclude_DATA = data
pkgdata_DATA = data
##pkglib_DATA = data
##pkginclude_DATA = data
## Standard directories: _SCRIPTS
## Commented out are invalid combinations.
bin_SCRIPTS = script
sbin_SCRIPTS = script
libexec_SCRIPTS = script
##data_SCRIPTS = script
##sysconf_SCRIPTS = script
##localstate_SCRIPTS = script
##lib_SCRIPTS = script
##info_SCRIPTS = script
##man_SCRIPTS = script
##include_SCRIPTS = script
##oldinclude_SCRIPTS = script
pkgdata_SCRIPTS = script
##pkglib_SCRIPTS = script
##pkginclude_SCRIPTS = script
EOF
set -e
$AUTOMAKE
# install-SCRIPTS targets.
sed -n '/^install-data-am/,/^ /p' Makefile.in > produced
cat > expected <<'EOF'
install-data-am: install-dataDATA install-incldataHEADERS \
install-pkgdataDATA install-pkgdataSCRIPTS
EOF
diff expected produced
# install-exec targets.
sed -n '/^install-exec-am/,/^ /p' Makefile.in > produced
cat > expected <<'EOF'
install-exec-am: install-binSCRIPTS install-inclexecHEADERS \
install-libexecSCRIPTS install-localstateDATA \
EOF
diff expected produced
exit 0
