cmd/go/internal/modget: support the suffix '@patch' in 'go get'

As of this change, an explicit '@patch' suffix is to '-u=patch' as
'@latest' is to '-u'.

RELNOTE='go get' in module mode now supports the version suffix '@patch'.

Fixes #26812

Change-Id: Ib5eee40de640440f7470d37a574b311ef8a67f67
Reviewed-on: https://go-review.googlesource.com/c/go/+/167747
Run-TryBot: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Jay Conrod <jayconrod@google.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/src/cmd/go/internal/modload/load.go b/src/cmd/go/internal/modload/load.go
index 57c2dd25a6..d55e0c5403 100644
--- a/src/cmd/go/internal/modload/load.go
+++ b/src/cmd/go/internal/modload/load.go
@@ -339,7 +339,7 @@ func loadAll(testAll bool) []string {
 	if !testAll {
 		loaded.testRoots = true
 	}
-	all := TargetPackages()
+	all := TargetPackages("...")
 	loaded.load(func() []string { return all })
 	WriteGoMod()
 
@@ -357,10 +357,11 @@ func loadAll(testAll bool) []string {
 // Only "ignore" and malformed build tag requirements are considered false.
 var anyTags = map[string]bool{"*": true}
 
-// TargetPackages returns the list of packages in the target (top-level) module,
-// under all build tag settings.
-func TargetPackages() []string {
-	return matchPackages("...", anyTags, false, []module.Version{Target})
+// TargetPackages returns the list of packages in the target (top-level) module
+// matching pattern, which may be relative to the working directory, under all
+// build tag settings.
+func TargetPackages(pattern string) []string {
+	return matchPackages(pattern, anyTags, false, []module.Version{Target})
 }
 
 // BuildList returns the module build list,