Add simple changelog generator

    $ oc adm release info --changelog=/tmp/git ...

Will generate an opinionated changelog in markdown from the payload.
It requires `oc adm release extract --git=DIR` to be invoked first,
and will scan for PR merge commits in those repos and expose them.
Issues that begin with `Bug [0-9]+: ` will be linked to bugzilla.

This will eventually also be able to print a list of bugs that can
be marked as part of the payload.

pkg/oc/cli/admin/release/extract.go

@@ -240,16 +240,10 @@ func (o *ExtractOptions) extractGit(dir string) error {
  }
  alreadyExtracted[repo] = commit
 
- u, err := sourceLocationAsURL(repo)
+ basePath, err := sourceLocationAsRelativePath(dir, repo)
  if err != nil {
  return err
  }
- gitPath := u.Path
- if strings.HasSuffix(gitPath, ".git") {
- gitPath = strings.TrimSuffix(gitPath, ".git")
- }
- gitPath = path.Clean(gitPath)
- basePath := filepath.Join(dir, u.Host, filepath.FromSlash(gitPath))
 
  var git *git
  fi, err := os.Stat(basePath)
@@ -341,14 +335,14 @@ func (g *git) basename() string {
 }
 
 func (g *git) CheckoutCommit(repo, commit string) error {
- _, err := g.exec("rev-parse", commit)
+ _, err := g.exec("show-ref", commit)
  if err == nil {
  return nil
  }
 
  // try to fetch by URL
  if _, err := g.exec("fetch", repo); err == nil {
- if _, err := g.exec("rev-parse", commit); err == nil {
+ if _, err := g.exec("show-ref", commit); err == nil {
  return nil
  }
  }
@@ -366,3 +360,17 @@ func sourceLocationAsURL(location string) (*url.URL, error) {
  }
  return url.Parse(location)
 }
+
+func sourceLocationAsRelativePath(dir, location string) (string, error) {
+ u, err := sourceLocationAsURL(location)
+ if err != nil {
+ return "", err
+ }
+ gitPath := u.Path
+ if strings.HasSuffix(gitPath, ".git") {
+ gitPath = strings.TrimSuffix(gitPath, ".git")
+ }
+ gitPath = path.Clean(gitPath)
+ basePath := filepath.Join(dir, u.Host, filepath.FromSlash(gitPath))
+ return basePath, nil
+}