From: Jeff King <peff@peff.net>
Date: Thu, 19 Jul 2018 21:47:30 GMT
Subject: Re: Find commit that referenced a blob first
Message-ID: <20180719214729.GA14323@sigill.intra.peff.net>
In-Reply-To: <CAGZ79kbJnyRbeH8yMa=QaqNofA_Ek_SwmH5qRaCaq4cyQ26Kqg@mail.gmail.com>

On Thu, Jul 19, 2018 at 02:19:34PM -0700, Stefan Beller wrote:

> > I have a blob hash and I would like to know what commit referenced
> > this blob first in a given Git repo.
> 
> git describe <blob>
> 
> If the given object refers to a blob, it will be described as
> <commit-ish>:<path>,
> such that the blob can be found at <path> in the <commit-ish>, which itself
> describes the first commit in which this blob occurs in a reverse
> revision walk from HEAD.
> 
> Since
> 644eb60bd01 (builtin/describe.c: describe a blob, 2017-11-15)
> (included first in 2.16.0

Hmm.

  $ git describe cfbc47ee2d
  fatal: No tags can describe '83adac3c57ad8cd2c8d44b525414b949950e316d'.
  Try --always, or create some tags.

  $ git describe --always cfbc47ee2d
  83adac3c57:checkout-cache.c

That first output confused me for a moment. We can't produce a nice
descriptive name for the commit in question, so we punt on the whole
thing.

Anyway. I have found your diff --find-object to be more useful in
practice. I.e.:

  git log --find-object=cfbc47ee2d

because I usually care less about a succinct name, and more about
digging into the history (so adding "-p", etc).

-Peff