LNT should have support for displaying the commit information associated to an order

[ldionne]

There should be a way to include commit information associated to an order when making a submission, and that commit information should be displayed on the graph directly (or at least visible when clicking on the order link).

Something akin to this UI (produced by https://github.com/llvm/llvm-project/blob/0d758de6fbbe5/libcxx/utils/visualize-historical)

[lukel97]

I think we also need to somehow make LNT Git SHA aware. At the moment if you want to the orders to make sense chronologically you manually need to specify it with something like git -C $LLVM_DIR rev-list --count HEAD.

My guess is that back in the SVN days this was easily inferred. But if we want to use a git SHA as an order directly we'll need to somehow have lnt lookup the commit date or something to sort it.

[ldionne]

Yeah, I've been thinking about that. I do really like the generality of a pure ordinal notion of order though, I think it's really neat and general. However, we could perhaps improve the input tools (e.g. lnt submit and/or lnt import and/or lnt importreport) to be git-aware. Perhaps all they need is an option to pass a git repository and to consider the order as a commit, and they'll generate an appropriate revlist-order based on that?

I was thinking that the general feature we want might be to mark a field in the database as "additional information to display on charts". Then, if you configure your database with a git_commit_info field marked as display, and if you import git show as the value for git_commit_info alongside your report, we'd have what we need. I'll need to play around with it a bit more.

Another side quest I'd like to eventually tackle is the elimination of llvm_project_revision as a hardcoded field in a bunch of places. I don't understand why that was hardcoded, LNT seemed much more general-purpose before that. But one thing at a time.