Mirroring of external repository does not work after rebase

[samangh]

• Gitea version (or commit ref): 1.8.0 built with go1.12.4
• Git version: 2.21.0
• Operating system: Linux Debian
• Database (use [x]):
  • [ x] MySQL
• Can you reproduce the bug at https://try.gitea.io:
  • [ x] Yes

Description

If gitea is mirroring an external repository and the external repository undergoes a rebase or a force push (so that the histories diverge), then the mirrored repository fails to show those changes.

Steps to reproduce:

1. Create a repository with an inital commit on GitHub
2. Mirror this with gitea
3. Reword the initial commit, and force push up to Github
4. Observe that the changes are not shown on the master branch of the mirrored repository

For an example please see https://try.gitea.io/samangh/teset, which is supposed to be a mirror of https://github.com/samangh/test.

Have you ever update the mirror settings on the settings page?

My mirror repo is getting weird after #6593 merged, can you check it? @zeripath

The mirror is unable to update the new commits to the proper branch after I update the mirror settings.

xxxxx.git/config:

before:

[core]
    ...
[remote "origin"]
	url = https://xxxx
	fetch  = +refs/*:refs/*
	mirror = true

after mirror settings updated:

[core]
    ...
[remote "origin"]
	url = https://xxxx
	fetch = +refs/heads/*:refs/remotes/origin/*

gitea/models/repo_mirror.go

Lines 123 to 133 in eb8632b

	func (m *Mirror) SaveAddress(addr string) error {
	repoPath := m.Repo.RepoPath()
	// Remove old origin
	_, err := git.NewCommand("remote", "remove", "origin").RunInDir(repoPath)
	if err != nil && !strings.HasPrefix(err.Error(), "exit status 128 - fatal: No such remote ") {
	return err
	}
	_, err = git.NewCommand("remote", "add", "origin", addr).RunInDir(repoPath)
	return err
	}

[samangh]

Have you ever update the mirror settings on the settings page?

No. I've just tried to manually mirror things by pressing the 'Sync' button.

Interesting, this is not 100% reproducible. I just setup another mirror on my local gitea server and the mirroring worked fine even with rebases. However, the example mirror that I setup on https://try.gitea.io/samangh/teset is still broken.

[zeripath]

Hmm... I wonder if this needs to be

_, err = git.NewCommand("remote", "add", "origin", "--mirror=fetch", addr).RunInDir(repoPath)