AmbiguousCommand is raised too soon. Right now, hg raises AmbiguousCommand as soon as it finds two commands/aliases that start with the substring it's searching for, even though it may still find a full match later on. This is a bit hard to hit on purpose, because hg checks the list of commands in whatever order is returned by table.keys(), which will change when you add an alias to a command. You should be able to hit it by adding an alias "u" to the "identify" command - not that that makes a lot of sense...

SOURCES=$(wildcard *.[0-9].txt)
MAN=$(SOURCES:%.txt=%)
HTML=$(SOURCES:%.txt=%.html)

all: man html

man: $(MAN)

html: $(HTML)

%: %.xml
	xmlto man $*.xml

%.xml: %.txt
	asciidoc -d manpage -b docbook $*.txt

%.html: %.txt
	asciidoc -b html4 $*.txt || asciidoc -b html $*.txt

clean:
	$(RM) $(MAN) $(MAN:%=%.xml) $(MAN:%=%.html)