git: fix pulling commit SHA only referenced from a tag

On commit SHA input we currently do a full fetch of
remote so we can pick up the commit by SHA later. This
only pulls in tags that are also part of branches. Extra
flag is needed to also get the tags that are not part of
branches.

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

source/git/source.go

@@ -470,6 +470,7 @@ func (gs *gitSourceHandler) Snapshot(ctx context.Context, g session.Group) (out
 		if !isCommitSHA(ref) { // TODO: find a branch from ls-remote?
 			args = append(args, "--depth=1", "--no-tags")
 		} else {
+			args = append(args, "--tags")
 			if _, err := os.Lstat(filepath.Join(gitDir, "shallow")); err == nil {
 				args = append(args, "--unshallow")
 			}