Re: [RFC PATCH] gitweb: use HEAD as primary sort key in git_get_heads_list()

From: Jeff King <peff@peff.net>
Date: Jun 8, 2021, 08:34 UTC
Message-ID: <YL8rjeKQPOtQSyzT@coredump.intra.peff.net>
In-Reply-To: <20210606085732.15001-1-greg@hurrell.net>

On Sun, Jun 06, 2021 at 10:57:32AM +0200, Greg Hurrell wrote:

Show 11 quoted lines

> Prior to this commit, the "heads" section on a gitweb summary page would
> list the heads in `-committerdate` order (ie. the most recently-modified
> ones at the top).
> 
> In my own repos I have started to move from "master" towards "main", but
> I keep "master" around and in sync with "main" so as not to break
> existing clones. As such, they always point at the same commit.
> 
> This means that in the "heads" listing of a gitweb instance, the display
> order ends up being determined by how `git for-each-ref` decides to
> tie-break "master" and "main"

Hmm. I'd have expected it to, because we start the list in lexicographic order. I suspect the sort we use simply isn't stable (in a simple 3-ref example I made, "main" did sort before "master" by default). That would be easy to fix, of course, but there may be value in using the HEAD rule anyway.

Show 17 quoted lines

> For example, right now on a sample repo, gitweb shows the heads in this
> order, even though "master" and "main" reference the same commit. The
> tie-breaking evidently isn't happening lexicographically:
> 
> - master
> - main
> - pu
> - next
> 
> So, this commit adds another `--sort` parameter to the `git
> for-each-ref` invocation in `git_get_heads_list()`, ensuring that the
> `HEAD` ref always ends up getting sorted to the top:
> 
> - main
> - master
> - pu
> - next

In your earlier example, it sounded like you were primarily concerned with breaking ties. But here it sounds like you're proposing putting the HEAD first _regardless_ of the committer timestamp.

I don't have a strong feeling either way on that. It may surface an older branch, but in general I'd expect the HEAD to be reasonably up-to-date (unless somebody has a weird workflow that does not really use it at all, and expects people to always clone with "-b" or whatever. We can probably discount that).

It doesn't help the stability of non-HEAD branches that are in ties. I.e., I wonder if this should be two separate patches:

  1. break ties by name, like:

       git for-each-ref --sort=refname --sort=-committerdate

  2. emphasize the HEAD branch, even if it isn't the newest:

       git for-each-ref --sort=refname --sort=-committerdate --sort=-HEAD

-Peff