Running autoupdate for any active freeciv branch (git clone https://github.com/freeciv/freeciv.git) results in an error like:
/usr/bin/m4:/tmp/au5cPMMa/ac.m4:1100: ERROR: end of file in string autoupdate: error: /usr/bin/m4 failed with exit status: 1 I'm on Debian Testing (Bullseye). I've tested with both autoupdate that Debian ships (autoconf-2.69) and one of self-compiled autoconf-2.70. - ML
