cmd/go: move fmtcmd's side effect to Showcmd
Currently, fmtcmd may have the side effect of updating
Builder.scriptDir, the logical working directory of the printed
script. If it does so, it also returns a two line command consisting
of both a "cd" into the new scriptDir and the original command.
When fmtcmd is used as part of Showcmd, that's fine, but fmtcmd is
also used in a handful of places to construct command descriptions
that are ultimately passed to Builder.reportCmd. In these cases, it's
surprising that fmtcmd has any side effects, but the bigger problem is
that reportCmd isn't expecting a two-line description and will print
it wrong in the output.
One option is to fix printing multi-line descriptions in reportCmd,
but we can fix the surprise side effect too by instead moving the
working directory update to Showcmd. With this CL, fmtcmd merely
consults the working directory to shorten it in the output and does
not update it.
For #62067.
Change-Id: I7808b279a430551f4ba51545417adf0bb132f931
Reviewed-on: https://go-review.googlesource.com/c/go/+/534857
Reviewed-by: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Austin Clements <austin@google.com>