go-git: transform revision for last observed tag

This ensures this strategy is backwards compatible as well, as I
accidentally forgot to do this for go-git in #404.

This lacks tests (as does the libgit2 implementation), and it would
probably be good to make them less dynamic as a follow up, as that's
how this slipped through the cracks.

Signed-off-by: Hidde Beydals <hello@hidde.co>

git/gogit/clone.go

@@ -128,13 +128,12 @@ func (g *Client) cloneTag(ctx context.Context, url, tag string, opts repository.
 
  ref := plumbing.NewTagReferenceName(tag)
  // check if previous revision has changed before attempting to clone
- if opts.LastObservedCommit != "" {
+ if lastObserved := git.TransformRevision(opts.LastObservedCommit); lastObserved != "" {
  head, err := getRemoteHEAD(ctx, url, ref, g.authOpts, authMethod)
  if err != nil {
  return nil, err
  }
-
- if head != "" && head == opts.LastObservedCommit {
+ if head != "" && head == lastObserved {
  c := &git.Commit{
  Hash: git.ExtractHashFromRevision(head),
  Reference: ref.String(),
@@ -364,11 +363,11 @@ func recurseSubmodules(recurse bool) extgogit.SubmoduleRescursivity {
 
 func getRemoteHEAD(ctx context.Context, url string, ref plumbing.ReferenceName,
  authOpts *git.AuthOptions, authMethod transport.AuthMethod) (string, error) {
- config := &config.RemoteConfig{
+ remoteCfg := &config.RemoteConfig{
  Name: git.DefaultRemote,
  URLs: []string{url},
  }
- remote := extgogit.NewRemote(memory.NewStorage(), config)
+ remote := extgogit.NewRemote(memory.NewStorage(), remoteCfg)
  listOpts := &extgogit.ListOptions{
  Auth: authMethod,
  CABundle: authOpts.CAFile,