Re: I use whatchanged!

From: Jeff King <peff@peff.net>
Date: Aug 25, 2025, 08:54 UTC
Message-ID: <20250825085428.GA367101@coredump.intra.peff.net>
In-Reply-To: <877byxbtiw.fsf@gmail.com>

On Wed, Aug 20, 2025 at 04:57:43PM -0400, Ben Zanin wrote:

Show 24 quoted lines

> When I test that by running it inside a working directory of the git
> repo as of commit c44beea485f0f2feaf460e2ac87fdd5608d63cf0 / v2.51.0, it
> looks like the output of `git whatchanged --pretty='%at'` and that of
> `git log --raw --no-merges --pretty='%at'` is almost identical but for
> the addition of a couple of extra timestamps in the output:
> 
>     diff -U0 \
>       <(git whatchanged --i-still-use-this --pretty='%at') \
>       <(git log --raw --no-merges --pretty='%at')
> 
> ...gives me..:
> 
>     --- /dev/fd/63  2025-08-20 16:55:36.936065126 -0400
>     +++ /dev/fd/62  2025-08-20 16:55:36.936065126 -0400
>     @@ -39,0 +40 @@
>     +1754972997
>     @@ -3773,0 +3775 @@
>     +1745540054
>     @@ -18102,0 +18105 @@
>     +1717188675
>     @@ -210119,0 +210123 @@
>     +1179951046
>     @@ -243728,0 +243733 @@
>     +1113865892

Looks like those are cases where the commit is empty (it's not a merge, and has the same tree as its first parent). E.g.:

  $ commits=8d2709d075d65ba386a4dac157129ef868c283e5^-
  $ git log --oneline --raw --no-merges $commits
  8d2709d075 A few hotfixes before -rc2

  $ git whatchanged --i-still-use-this $commits
  [no output]

The culprit is the revs.always_show_header flag, which git-log sets but git-whatchanged does not. I don't think there is a way to influence it with an option, though. You can simplify history by giving a pathspec, but that can have broader changes (e.g., it may also simplify away side branches).

I don't know if that's an option that should be added before declaring whatchanged dead. Arguably the git-log behavior is much more reasonable, but I don't know if anybody cares about being byte-for-byte identical to whatchanged behavior.

-Peff