So the optimization to avoid hg clone works again. The
builder looks at buildroot+"goroot" for an hg clone repo. If
it finds it, it can just "hg pull" instead of a slow "hg
clone".
LGTM=cmang
R=cmang, proppy
CC=golang-codereviews
https://golang.org/cl/147960044
... since it already caught a problem and was fixed in
hg rev 0b99c2137ccc.
I pushed this live already just so don't get a whole column of
fail that might hide other issues. Real users have USER set
anyway. (Perhaps we should set it for all our builders?)
LGTM=adg
R=golang-codereviews
CC=adg, dave, golang-codereviews, minux
https://golang.org/cl/137180043