Support fetching/checkouts of non-branch/-tag git refs (argoproj#322)

* Support fetching/checkouts of non-branch/-tag git refs

Provides a `source.git.ref` field for specifying a specific non-branch
non-tag git ref at which to perform a checkout. Providing one will
result in a shallow (depth 1) clone of the repo and shallow subsequent
fetches.

The motivation for this change is to support sourcing of trigger
templates from Gerrit patchsets. Gerrit uses non-branch/-tag refs
extensively and specifically in this case stores change patchsets in
`refs/changes/[slice]/[change]/[patchset]`. While arbitrary refs are
kind of an obscure git feature, there very well may be other git based
systems utilizing them.

* Fixed protobuf field index for Ref

pkg/apis/sensor/v1alpha1/types.go

@@ -466,10 +466,15 @@ type GitArtifact struct {
  // +optional
  Tag string `json:"tag,omitempty" protobuf:"bytes,8,opt,name=tag"`
 
+ // Ref to use to pull trigger resource. Will result in a shallow clone and
+ // fetch.
+ // +optional
+ Ref string `json:"ref,omitempty" protobuf:"bytes,9,opt,name=ref"`
+
  // Remote to manage set of tracked repositories. Defaults to "origin".
  // Refer https://git-scm.com/docs/git-remote
  // +optional
- Remote *GitRemoteConfig `json:"remote" protobuf:"bytes,9,opt,name=remote"`
+ Remote *GitRemoteConfig `json:"remote" protobuf:"bytes,10,opt,name=remote"`
 }
 
 // GitRemoteConfig contains the configuration of a Git remote

store/git.go

@@ -138,6 +138,13 @@ func (g *GitArtifactReader) readFromRepository(r *git.Repository) ([]byte, error
  fetchOptions.Auth = auth
  }
 
+ // In the case of a specific given ref, it isn't necessary to fetch anything
+ // but the single ref
+ if g.artifact.Ref != "" {
+ fetchOptions.Depth = 1
+ fetchOptions.RefSpecs = []config.RefSpec{config.RefSpec(g.artifact.Ref + ":" + g.artifact.Ref)}
+ }
+
  if err := r.Fetch(fetchOptions); err != nil && err != git.NoErrAlreadyUpToDate {
  return nil, fmt.Errorf("failed to fetch. err: %v", err)
  }
@@ -146,17 +153,20 @@ func (g *GitArtifactReader) readFromRepository(r *git.Repository) ([]byte, error
  return nil, fmt.Errorf("failed to checkout. err: %+v", err)
  }
 
- pullOpts := &git.PullOptions{
- RecurseSubmodules: git.DefaultSubmoduleRecursionDepth,
- ReferenceName: g.getBranchOrTag().Branch,
- Force: true,
- }
- if auth != nil {
- pullOpts.Auth = auth
- }
+ // In the case of a specific given ref, it shouldn't be necessary to pull
+ if g.artifact.Ref != "" {
+ pullOpts := &git.PullOptions{
+ RecurseSubmodules: git.DefaultSubmoduleRecursionDepth,
+ ReferenceName: g.getBranchOrTag().Branch,
+ Force: true,
+ }
+ if auth != nil {
+ pullOpts.Auth = auth
+ }
 
- if err := w.Pull(pullOpts); err != nil && err != git.NoErrAlreadyUpToDate {
- return nil, fmt.Errorf("failed to pull latest updates. err: %+v", err)
+ if err := w.Pull(pullOpts); err != nil && err != git.NoErrAlreadyUpToDate {
+ return nil, fmt.Errorf("failed to pull latest updates. err: %+v", err)
+ }
  }
 
  return ioutil.ReadFile(fmt.Sprintf("%s/%s", g.artifact.CloneDirectory, g.artifact.FilePath))
@@ -173,6 +183,9 @@ func (g *GitArtifactReader) getBranchOrTag() *git.CheckoutOptions {
  if g.artifact.Tag != "" {
  opts.Branch = plumbing.NewTagReferenceName(g.artifact.Tag)
  }
+ if g.artifact.Ref != "" {
+ opts.Branch = plumbing.ReferenceName(g.artifact.Ref)
+ }
 
  return opts
 }
@@ -197,6 +210,12 @@ func (g *GitArtifactReader) Read() ([]byte, error) {
  cloneOpt.Auth = auth
  }
 
+ // In the case of a specific given ref, it isn't necessary to have branch
+ // histories
+ if g.artifact.Ref != "" {
+ cloneOpt.Depth = 1
+ }
+
  r, err = git.PlainClone(g.artifact.CloneDirectory, false, cloneOpt)
  if err != nil {
  return nil, fmt.Errorf("failed to clone repository. err: %+v", err)

store/git_test.go

@@ -94,4 +94,10 @@ func TestGetBranchOrTag(t *testing.T) {
  tag := gar.getBranchOrTag()
  convey.So(tag.Branch, convey.ShouldNotEqual, "refs/heads/master")
  })
+
+ convey.Convey("Given a git artifact with a specific ref, get the ref", t, func() {
+ gar.artifact.Ref = "refs/something/weird/or/specific"
+ br := gar.getBranchOrTag()
+ convey.So(br.Branch, convey.ShouldEqual, "refs/something/weird/or/specific")
+ })
 }