tree c9aba1c24e239108f67af82421c22f6bb786ba9a
parent 3579ffcf11c94d03d3f236a7bbe3d1e4533bacd2
author Russ Cox <rsc@golang.org> 1524025940 -0400
committer Russ Cox <rsc@golang.org> 1524669555 +0000

cmd/go/internal/modfetch: make gopkg.in support more seamless

Gopkg.in did semantic import versioning first.
We should make it as easy as possible for users
of gopkg.in to migrate to vgo.

Before this CL, gopkg.in was supported as a special
kind of code fetcher that rewrote tags to add a funny
prefix, so that gopkg.in/russross/blackfriday.v2 v2.0.0
showed up in go.mod as

	gopkg.in/russross/blackfriday.v2 v1.0.0-gopkgin-v2.0.0

This was needed because by the usual module path syntax
rules, gopkg.in/russross/blackfriday.v2 should be a v1 of
a package. But it's rather mysterious.

Instead, as a nod to gopkg.in being here first, this CL changes
the module path syntax rules to understand the version ranges
for a given gopkg.in path, allowing the expected:

	gopkg.in/russross/blackfriday.v2 v2.0.0

It even supports .v1 paths correctly.

The version fixer recognizes the old v1.0.0-gopkgin-v2.0.0
and turns it into plain v2.0.0.

Fixes golang/go#23991.
Fixes golang/go#24099.

Change-Id: I579863c2d36780bd1e9f1b786f41560bd774d8e3
Reviewed-on: https://go-review.googlesource.com/107658
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>