Such messages are more informative when the error occurs deep within a script.
Also: add tool name to digraph's usage messages.
LGTM=gri
R=gri
CC=golang-codereviews
https://golang.org/cl/173380043
Rewrite performed with this command:
sed -i '' 's_code.google.com/p/go\._golang.org/x/_g' \
$(grep -lr 'code.google.com/p/go.' *)
LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/170920043
e.g. chmod +w, checkout.
Also: add a TIPS section to the documentation.
LGTM=crawshaw
R=crawshaw, gri
CC=golang-codereviews
https://golang.org/cl/136780044