v1.6.0 - testscript improvements

New features in this release:

• add ${/} as a companion to ${:} (#90; thanks to @mvdan)
• add Env.Setenv and Env.Getenv (#96; thanks to @twpayne)
• support stdout/stderr args in stdin (#94; thanks to @mvdan)
• expose current subtest in Env (#95; thanks to @frankban)

Also apply fix to lockedfile to fix #91 (thanks to @myitcv)

v1.5.2

• testscript: provide WorkdirRoot as a new Params field (#87) bc89b17
• testscript: fix race in setupfilenames test (#88) ae313c1

v1.5.1

• testscript: fail a test when a testscript Dir contains no scripts (#85) bf08ea5

v1.3.2

• testscript: make sure work dir isn't removed when -testwork is used (#80) 18d060b
• testscript: ensure that temp dir isn't sym-linked (#79) 9181448

v1.3.1

• ci: changes for go1.13beta1 0483ff7
• modfile: add tests for AddReplace and DropReplace (#72) 3670dca
• Merge pull request #71 from rogpeppe/023-fmtsort 6f68bf1

v1.2.2

cmd/testscript: add support to pass through env vars with -e (#54)

v1.2.1

testscript: only expand second argument to cmpenv (#53)

v1.1.1-alpha

testscript: respect TestScript env PATH variable for exec command (#49)

Includes a partial snapshot of os/exec's platform-specific LookPath
logic, as of 0456036e28b718d215f49abe83d3c49101f8a4c7. This is largely a
copy and paste, with a type alias to os/exec.Error and an "alias" of
os/exec.ErrNotFound.

v1.0.1-alpha.6

Includes first cut of cmd/testscript. See https://github.com/rogpeppe/go-internal/blob/master/cmd/testscript/README.md for more details.

v1.0.1-alpha.5

cmd/testscript: minor bug fixes (#44)