This patch adds a place for tracking the current `HEAD` commit in the
underlying Git repo. It updates `git::import_refs()` to record it. We
don't use it anywhere yet.
This is part of #44.
I've finally decided to copy Git's branching model (issue #21), except
that I'm letting the name identify the branch across
remotes. Actually, now that I think about, that makes them more like
Mercurial's "bookmarks". Each branch will record the commit it points
to locally, as well as the commits it points to on each remote (as far
as the repo knows, of course). Those records are effectively the same
thing as Git's "remote-tracking branches"; the difference is that we
consider them the same branch. Consequently, when you pull a new
branch from a remote, we'll create that branch locally.
For example, if you pull branch "main" from a remote called "origin",
that will result in a local branch called "main", and also a record of
the position on the remote, which we'll show as "main@origin" in the
CLI (not part of this commit). If you then update the branch locally
and also pull a new target for it from "origin", the local "main"
branch will be divergent. I plan to make it so that pushing "main"
will update the remote's "main" iff it was currently at "main@origin"
(i.e. like using Git's `git push --force-with-lease`).
This commit adds a place to store information about branches in the
view model. The existing git_refs field will be used as input for the
branch information. For example, we can use it to tell if
"refs/heads/main" has changed and how it has changed. We will then use
that ref diff to update our own record of the "main" branch. That will
come later. In order to let git_refs take a back seat, I've also added
tags (like Git's lightweight tags) to the model in this commit.
I haven't ruled out *also* having some more persistent type of
branches (like Mercurials branches or topics).
When there are two concurrent operations, we would resolve conflicting
updates of git refs quite arbitrarily before this change. This change
introduces a new `refs` module with a function for doing a 3-way merge
of ref targets. For example, if both sides moved a ref forward but by
different amounts, we pick the descendant-most target. If we can't
resolve it, we leave it as a conflict. That's fine to do for git refs
because they can be resolved by simply running `jj git refresh` to
import refs again (the underlying git repo is the source of truth).
As with the previous change, I'm doing this now because mostly because
it is a good stepping stone towards branch support (issue #21). We'll
soon use the same 3-way merging for updating the local branch
definition (once we add that) when a branch changes in the git repo or
on a remote.
This adds support for having conflicting git refs in the view, but we
never create conflicts yet. The `git_refs()` revset includes all "add"
sides of any conflicts. Similarly `origin/main` (for example) resolves
to all "adds" if it's conflicted (meaning that `jj co origin/main` and
many other commands will error out if `origin/main` is
conflicted). The `git_refs` template renders the reference for all
"adds" and adds a "?" as suffix for conflicted refs.
The reason I'm adding this now is not because it's high priority on
its own (it's likely extremely uncommon to run two concurrent `jj git
refresh` and *also* update refs in the underlying git repo at the same
time) but because it's a building block for the branch support I've
planned (issue #21).
When using the command line interface (which is the only interface so
far), it seems more useful to see the exact command that was run than
a logical description of what it does. This patch makes the CLI record
that information in the operation metadata in a new key/value field. I
put it in a generic key/value field instead of a more specialized
field because the key/value field seems like a useful thing to have in
general. However, that means that we "have to" do shell-escaping when
saving the data instead of leaving the data unescaped and adding the
shell-escaping when presenting it. I added very simple shell-escaping
for now.
This continues the work to make the `View` types be only about the
state of the current view and not about operations in general (which
has been moved out `OpStore` and qOpHeadsStore`).
Mercurial's "phase" concept is important for evolution, and it's also
useful for filtering out uninteresting commits from log
output. Commits are typically marked "public" when they are pushed to
a remote. The CLI prevents public commits from being rewritten. Public
commits cannot be obsolete (even if they have a successor, they won't
be considered obsolete like non-public commits would).
This commits just makes space for tracking the public heads in the
View.
Git refs are important at least for understanding where the remote
branches are. This commit adds support for tracking them in the view
and makes `git::import_refs()` update them.
When merging views (either because of concurrent operations or when
undoing an earlier operation), there can be conflicts between git ref
changes. I ignored that for now and let the later operation win. That
will probably be good enough for a while. It's not hard to detect the
conflicts, but I haven't yet decided how to handle them. I'm leaning
towards representing the conflicting refs in the view just like how we
represent conflicting files in the tree.
