internal/testenv: check that external 'diff' tool is the GNU version

TestVerifyUnified in internal/lsp/diff/difftest requires specific
behaviour of the 'diff' command which is known to be satisfied by
GNU diff. The plan9 'diff' command has no '-u' option, and the
illumos 'diff -u' produces output in a different format. Checking
specifically for the GNU version in the HasTool function ensures
the expected behaviour, and otherwise causes the test to be skipped.

Updates golang/go#38772

Change-Id: I5493fa8cfc48a112dc0b7356618c62d3ccb0366f
Reviewed-on: https://go-review.googlesource.com/c/tools/+/232479
Reviewed-by: Ian Cottrell <iancottrell@google.com>
Run-TryBot: Rebecca Stambler <rstambler@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2 files changed
tree: 231fc4391b2622ded827375405af2fbb84c70b34
  1. benchmark/
  2. blog/
  3. cmd/
  4. container/
  5. cover/
  6. go/
  7. godoc/
  8. gopls/
  9. imports/
  10. internal/
  11. playground/
  12. present/
  13. refactor/
  14. txtar/
  15. .gitattributes
  16. .gitignore
  17. AUTHORS
  18. codereview.cfg
  19. CONTRIBUTING.md
  20. CONTRIBUTORS
  21. go.mod
  22. go.sum
  23. LICENSE
  24. PATENTS
  25. README.md
README.md

Go Tools

This subrepository holds the source for various packages and tools that support the Go programming language.

Some of the tools, godoc and vet for example, are included in binary Go distributions.

Others, including the Go guru and the test coverage tool, can be fetched with go get.

Packages include a type-checker for Go and an implementation of the Static Single Assignment form (SSA) representation for Go programs.

Download/Install

The easiest way to install is to run go get -u golang.org/x/tools/.... You can also manually git clone the repository to $GOPATH/src/golang.org/x/tools.

Report Issues / Send Patches

This repository uses Gerrit for code changes. To learn how to submit changes to this repository, see https://golang.org/doc/contribute.html.

The main issue tracker for the tools repository is located at https://github.com/golang/go/issues. Prefix your issue with “x/tools/(your subdir):” in the subject line, so it is easy to find.