cmd/go: add '--' before repository names when invoking vcs tools

Also, in 'go get' in GOPATH mode, report an error for package paths
that start with '-'.

Change-Id: Ic2575381aa2d093ba15c53b893bf2eaded8b6066
Reviewed-on: https://go-review.googlesource.com/c/go/+/181237
Run-TryBot: Jay Conrod <jayconrod@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/src/cmd/go/internal/modfetch/codehost/git.go b/src/cmd/go/internal/modfetch/codehost/git.go
index 272eadcb23..a1d451d61a 100644
--- a/src/cmd/go/internal/modfetch/codehost/git.go
+++ b/src/cmd/go/internal/modfetch/codehost/git.go
@@ -80,7 +80,7 @@ func newGitRepo(remote string, localOK bool) (Repo, error) {
 			// but this lets us say git fetch origin instead, which
 			// is a little nicer. More importantly, using a named remote
 			// avoids a problem with Git LFS. See golang.org/issue/25605.
-			if _, err := Run(r.dir, "git", "remote", "add", "origin", r.remote); err != nil {
+			if _, err := Run(r.dir, "git", "remote", "add", "origin", "--", r.remote); err != nil {
 				os.RemoveAll(r.dir)
 				return nil, err
 			}
@@ -123,8 +123,10 @@ type gitRepo struct {
 	statCache par.Cache
 
 	refsOnce sync.Once
-	refs     map[string]string
-	refsErr  error
+	// refs maps branch and tag refs (e.g., "HEAD", "refs/heads/master")
+	// to commits (e.g., "37ffd2e798afde829a34e8955b716ab730b2a6d6")
+	refs    map[string]string
+	refsErr error
 
 	localTagsOnce sync.Once
 	localTags     map[string]bool
@@ -407,7 +409,7 @@ func (r *gitRepo) fetchUnshallow(refSpecs ...string) error {
 // statLocal returns a RevInfo describing rev in the local git repository.
 // It uses version as info.Version.
 func (r *gitRepo) statLocal(version, rev string) (*RevInfo, error) {
-	out, err := Run(r.dir, "git", "-c", "log.showsignature=false", "log", "-n1", "--format=format:%H %ct %D", rev)
+	out, err := Run(r.dir, "git", "-c", "log.showsignature=false", "log", "-n1", "--format=format:%H %ct %D", rev, "--")
 	if err != nil {
 		return nil, fmt.Errorf("unknown revision %s", rev)
 	}