sim: replacing ChangeLog files with online git logs

[Paul Smith]

On Sat, 2021-03-13 at 13:21 -0500, Mike Frysinger via Gdb wrote:
> > > the hard & bikeshed part is what form does the log take.  do you
> > > just want the default `git log` output ?
> > There's a Gnulib script which will produce the form that matches
> > the ChangeLog format.
> 
> there's actually multiple gnulib scripts.  which one are you
> referring to ? gitlog-to-changelog ?

I have no interest in getting in the middle of the discussion on what
is appropriate or not, but FYI this is the text I add to the maintainer
version of the makefile for GNU make, if it helps (the gl2cl-date
variable holds the oldest date to be included in the ChangeLog).


## ---------------------- ##
## Generating ChangeLog.  ##
## ---------------------- ##

gl2cl-date := 2013-10-10
gl2cl := $(GNULIBDIR)/build-aux/gitlog-to-changelog

# Rebuild the changelog whenever a new commit is added
ChangeLog: .check-git-HEAD
	if test -f '$(gl2cl)'; then \
	    '$(gl2cl)' --since='$(gl2cl-date)' > '$@'; \
	else \
	    echo "WARNING: $(gl2cl) is not available.  No $@ generated."; \
	fi

.check-git-HEAD: FORCE
	sha="`git rev-parse HEAD`"; \
	test -f '$@' && [ "`cat '$@' 2>/dev/null`" = "$$sha" ] \
	    || echo "$$sha" > '$@'

.PHONY: FORCE
FORCE:;@: