git-describe

[fenollp]

I see in COMPATIBILITY.md that describe is neither supported nor unsupported (empty box). I also see that there are no implementation containing that name.

1. If it is implemented, could you point me to the right function?
2. If not, any plans on supporting it?

I am looking for the equivalent of git describe --abbrev --dirty --always --tags.

Maybe related: https://github.com/src-d/go-git/issues/599 https://github.com/src-d/go-git/pull/139 Keep up the amazing work!

[edupo]

This feature will be helpful for us so I started writing something.

My idea was to get the log of the HEAD and check each commit against the tag pool until a match... But I see some issue with the tag check:

• Initially I went for the repo.TagObject(commit.Hash) when walking down the log. But TagObject only returns annotated tags and for git describe --tags that is not a problem.

• The approach I take now is to iterate through all tags like:

      // Opening the repo
      cwd , err := filepath.Abs(".")
      PanicIfError(err)
      r, err := git.PlainOpen(cwd)
      PanicIfError(err)
  
      // Head
      head, err := r.Head()
      PanicIfError(err)
      cIter, err := r.Log(&git.LogOptions{
          From: head.Hash(),
          Order: git.LogOrderCommitterTime,
      })
  
      var tag *plumbing.Reference
      err = cIter.ForEach(func(c *object.Commit) error {
          // Tags
          tags, err := r.Tags()
          PanicIfError(err)
  
          err = tags.ForEach(func(t *plumbing.Reference) error {
  
              t_hash := t.Hash()
              fmt.Printf("%v - %v\n", c.Hash, t_hash)
  
              if bytes.Equal(c.Hash[:] ,t_hash[:]) {
                  // Found!
                  tag = t;
                  return storer.ErrStop
              }
              // No luck continue searching.
              return nil
          })
          if tag != nil {
              // Found
              return storer.ErrStop
          }
          // Not found!
          return nil
      })
      PanicIfError(err)

  But this is no good solution for repositories where thousands of tags exists.

• Further development will be to make a map during the first iteration but for optimizing that I will create a wrapper class around git to hold the map for queries in my app and reuse it as much as possible.

From here is not hard to create a proto describe using the tag, the number of new commits from the tag and the hash of the head...

[edupo]

Here is my basic implementation of a git describe with the idea of a map and a wrapper struct for go-git.

https://github.com/edupo/semver-cli/blob/master/gitWrapper/git.go

I'm not an expert on the matter but if this solution works for others I may do a PR on the go-git. (If I ever understand the million details required to contribute... xD)

[mcuadros]

PRs are more than welcome.