Gerrit to GitHub migration

TLDR: Gerrit patches will be migrated to GitHub pull requests on Wednesday, May 8.

We will migrate the remaining Gerrit changesets as GitHub pull requests and will use GitHub pull requests for future changes to Charm++. We plan to do the migration on Wednesday, May 8.

The following steps will be taken:

1. Set the Charm++ Gerrit to readonly.
2. Rename the charm branch to master on GitHub.
3. Migrate changesets to GitHub.
4. Enable Travis CI builds on GitHub.
5. Modify autobuild to use GitHub.

About 200 open (i.e., not merged or abandoned) changesets will be migrated.

The pull requests will be created as branches on top of the master branch. The branches will be named review//.

Pull requests will be created as the user that created the changeset on Gerrit, as long as we have the GitHub username and token (as pplimport otherwise), similar to the issue migration from Redmine. We can reuse the previous tokens, no need to send us new information.

After migration, the Charm++ Gerrit will remain online in read-only mode for some time.

Note that only the changesets will be migrated, not the comments or reviews on Gerrit. Migrated pull requests will have a link back to Gerrit.

Things that you could do:

• Please familiarize yourself with how pull requests work. Pull requests use a branch granularity instead of the commit granularity that Gerrit uses. Apart from this difference, most concepts are very similar between pull requests and changesets. I wrote a brief overview of how pull requests work here: https://github.com/UIUC-PPL/charm/wiki/Working-with-GitHub-Pull-Requests
• We have already migrated the Gerrit changesets of Projections to GitHub (https://github.com/UIUC-PPL/projections). A test import of Charm++ Gerrit can be found here: https://github.com/UIUC-PPL/charm-test
• Please merge or abandon changes, if possible. This will reduce the number of changes that have to be transferred.