cmd/go: avoid accidental downgrades in 'go get' with latest and patch

Currently, 'go get -u' and 'go get -u=patch' avoid accidentally
downgrading modules by preventing upgrades in two cases:

1) If the current version is a prerelease that is semantically later
   than the "latest" or "patch" version.
2) If the current version is a pseudoversion that is chronologically
   newer than the "latest" or "patch" version.

With this change, 'go get m@latest' and 'go get m@patch' prevent
downgrades using the same checks.

Also: 'go get m@patch' now works if m is a module path but not a
package path (i.e., there is no package in the module root directory).

Fixes #30634
Fixes #32537

Change-Id: I916630c385b5f3ba7c13e0d65ba08f73a1a67829
Reviewed-on: https://go-review.googlesource.com/c/go/+/180337
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/cmd/go/internal/mvs/mvs.go b/src/cmd/go/internal/mvs/mvs.go
index 04273e733c..dca909e858 100644
--- a/src/cmd/go/internal/mvs/mvs.go
+++ b/src/cmd/go/internal/mvs/mvs.go
@@ -35,7 +35,7 @@ type Reqs interface {
 	// Max returns the maximum of v1 and v2 (it returns either v1 or v2).
 	//
 	// For all versions v, Max(v, "none") must be v,
-	// and for the tanget passed as the first argument to MVS functions,
+	// and for the target passed as the first argument to MVS functions,
 	// Max(target, v) must be target.
 	//
 	// Note that v1 < v2 can be written Max(v1, v2) != v1