Add gerrit support

[guyzmo]

[framawiki]

Note: tracked on @wikimedia's phabricator too: https://phabricator.wikimedia.org/T180962

[nikitavbv]

I claimed this task on @wikimedia's phabricator and working on it now

[guyzmo]

Hey @Phantom-42, let's have a little discussion over here about the UX design of this PR. Currently you've implemented the following:

git gerrit request <project> create [--opts]
git gerrit request <project> fetch <ref>

usually, when adding a new service, what I start with are the basic operations:

• get a project (clone)
• create a new project (create),
• delete an existing project (delete),
• add service's remote to current project (add),
• fork the project (fork)

then I might play with some tougher APIs:

• list projects (list)
• handle snippets/gists (when supported)
• handle requests (create/fetch)

Now given the nature of gerrit, things might happen differently with it. But the questions are:

• how to match gerrit's workflow with the above toolbox, and
• what would be missing to add in that toolbox?

I believe that feedback work (generally speaking, commenting/reading/acting on issues (#104) and PRs) is the next must-have feature of git-repo, but it's tough to actually design it right.

so as you're working on it, @Phantom-42, may I ask you for your opinion? (and @jayvdb as well, of course).

[nikitavbv]

Well, the most actively used functions (clone, patchset pushing / reviewing, changes list) are already implemented. Other frequently used functions will come soon.

create, delete, fork, add are basic operations, but we skipped them for now as these functions are used rarely.

There are not snippets/gists/etc on Gerrit, however we need to focus on developing functionality related to patchset reviewing instead.

I will think more about this and will notify if I have any thoughts.
Anyway, I believe @jayvdb has far more ideas about this.

[guyzmo]

I've had a thought about interactions. As far as I remember last time I used gerrit (that was when I contributed some patches to some obscure Qt library), the process was:

• add the gerrit remote to my local repository ;
• create a new request on gerrit ; (or fetches one from gerrit)
• add the remote ref and pull it as a branch locally ;
• push -f my changes to that remote ref up until patchset review is approved and over ;

so how I'd see things, that would be:

# I got a bunch of commit to submit for reviewing
git gerrit add            # adds the gerrit remote to the current local repository
git gerrit request create # creates and fetches a new request as local ref
git co local/refs/of/patchset/being/reviewed
# make changes
git push -f gerrit

or

# I got a bunch of commit to submit for reviewing
git gerrit add               # adds the gerrit remote to the current local repository
git gerrit request list      # lists the requests being reviewed
git gerrit request fetch refs/of/patchset/being/reviewed # fetches a patchset to review
git co local/refs/of/patchset/being/reviewed
# make changes
git push -f gerrit

also, a nice to have feature, even though it's definitely not a must have, would be the git gerrit list feature (to list all projects of the current user). Why I like that feature, it's because I often use it to check that my credentials still work for a given service ;)