Re: git show -m with a parent number

From: Jeff King <peff@peff.net>
Date: Mar 28, 2016, 19:16 UTC
Message-ID: <20160328191608.GA22602@sigill.intra.peff.net>
In-Reply-To: <nd9gq6$412$1@ger.gmane.org>

On Sun, Mar 27, 2016 at 08:46:02PM +0000, Anatoly Borodin wrote:

> is there a good reason for `git show -m` to not accept the number of a
> parent of a merge commit? I can run `git show --first-parent COMMIT`,
> but need to write `git diff COMMIT^2 COMMIT` every time I want to diff
> with the second parent!

I think it could, but nobody has yet found it useful enough to implement.

I am not sure of the workflow it would help. Personally, I use "-m" in two situations:

  1. To puzzle out issues where "-c" or "--cc" do not show what I
     expected.

  2. With "--first-parent", to follow the linear history of a mainline
     branch, showing merged topic branches as a single diff.

For the first one, showing all diffs is what I want. For the second, it only makes sense to for the first parent case, as following other parents would zig-zag through history.

But perhaps you have some other use case in mind. In cases like these, I think it is a good idea to implement the feature, and run with it for a while, seeing how it can be used. And then if it proves useful, post the patch to the list describing your experiences.

-Peff