cmd/gorelease: infer base version if unspecified

If the -base flag is not set on the command line, it is now inferred
from the -version flag and available versions. If the -version flag is
given, the base version will be the highest available release version
lower than -version. Otherwise, the base version will be the highest
release version. Pre-release versions are not considered.

If there are no appropriate versions, and the release version is
unspecified or appears to be the first release (e.g., v0.1.0, v2.0.0),
the inferred base version will be "none" (meaning no comparison will
be made). Otherwise, an error will be shown.

Updates golang/go#26420

Change-Id: Iee45a4183f3e4a219c02a69b5d16a3cc5478644c
Reviewed-on: https://go-review.googlesource.com/c/exp/+/216078
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
15 files changed
tree: a8f1c0d2c45aa4bf71b3f487cea5f73231f45e57
  1. .gitattributes
  2. .gitignore
  3. AUTHORS
  4. CONTRIBUTING.md
  5. CONTRIBUTORS
  6. LICENSE
  7. PATENTS
  8. README.md
  9. apidiff/
  10. cmd/
  11. codereview.cfg
  12. ebnf/
  13. ebnflint/
  14. errors/
  15. fsnotify/
  16. go.mod
  17. go.sum
  18. inotify/
  19. io/
  20. mmap/
  21. rand/
  22. shiny/
  23. shootout/
  24. sumdb/
  25. utf8string/
  26. winfsnotify/
README.md

exp

This subrepository holds experimental and deprecated (in the old directory) packages.

The idea for this subrepository originated as the pkg/exp directory of the main repository, but its presence there made it unavailable to users of the binary downloads of the Go installation. The subrepository has therefore been created to make it possible to go get these packages.

Warning: Packages here are experimental and unreliable. Some may one day be promoted to the main repository or other subrepository, or they may be modified arbitrarily or even disappear altogether.

In short, code in this subrepository is not subject to the Go 1 compatibility promise. (No subrepo is, but the promise is even more likely to be violated by go.exp than the others.)

Caveat emptor.