Re: [PATCH 10/10] get_short_sha1: list ambiguous objects on error

From: Jeff King <peff@peff.net>
Date: Sep 29, 2016, 13:03 UTC
Message-ID: <20160929130322.562ng4t2ktk6qzok@sigill.intra.peff.net>
In-Reply-To: <2242637D-4C3B-4AF2-8BE4-823B3E1745D5@gmail.com>

On Thu, Sep 29, 2016 at 04:46:19AM -0700, Kyle J. McKay wrote:

Show 23 quoted lines

> This hint: information is excellent.  There needs to be a way to show it on
> demand.
> 
> $ git rev-parse --disambiguate=b2e1
> b2e11962c5e6a9c81aa712c751c83a743fd4f384
> b2e11d1bb40c5f81a2f4e37b9f9a60ec7474eeab
> b2e163272c01aca4aee4684f5c683ba341c1953d
> b2e18954c03ff502053cb74d142faab7d2a8dacb
> b2e1895ca92ec2037349d88b945ba64ebf16d62d
> 
> Not nearly so helpful, but the operation of --disambiguate cannot be changed
> without breaking current scripts.
> 
> Can your excellent "hint:" output above be attached to the --disambiguate
> option somehow, please.  Something like this perhaps:
> 
> $ git rev-parse --disambiguate-list=b2e1
> b2e1196 tag v2.8.0-rc1
> b2e11d1 tree
> b2e1632 commit 2007-11-14 - Merge branch 'bs/maint-commit-options'
> b2e1759 blob
> b2e18954 blob
> b2e1895c blob

I think the "right" way to do this is pipe the list of sha1s into another git commit which can format them however you want. Unfortunately, there isn't a single command that does a great job:

  - "cat-file --batch-check" can show you the sha1 and type, but it
    won't abbreviate sha1s, and it won't show you commit/tag information

  - "log --stdin --no-walk" will format the commit however you like, but
    skips the trees and blobs entirely, and the tag can only be seen via
    "%d"

  - "for-each-ref" has flexible formatting, too, but wants to format
    refs, not objects (and doesn't read from stdin).

IMHO that is a sign that our formatting tools aren't as good as they could be (I think the right tool is cat-file, but it should be able to do all of the formatting that the other commands can do).

Of course if you really just want human-readable output, then:

  $ git cat-file -e b2e1
  error: short SHA1 b2e1 is ambiguous
  hint: The candidates are:
  hint:   b2e1196 tag v2.8.0-rc1
  hint:   b2e11d1 tree
  hint:   b2e1632 commit 2007-11-14 - Merge branch 'bs/maint-commit-options'
  hint:   b2e1759 blob
  hint:   b2e18954 blob
  hint:   b2e1895c blob
  fatal: Not a valid object name b2e1

is pretty easy.

That being said, I don't mind if somebody wanted to do a rev-parse option on top of my series. The formatting code is already split into its own function.

-Peff