Re: ':/<oneline prefix>' notation doesn't support full file syntax

From: Junio C Hamano <gitster@pobox.com>
Date: Jul 3, 2008, 21:26 UTC
Message-ID: <7v7ic2zmjp.fsf@gitster.siamese.dyndns.org>
In-Reply-To: <56b7f5510807031127j10e33f3bl516180f7a9b5b5db@mail.gmail.com>

"Dana How" <danahow@gmail.com> writes:

Show 5 quoted lines

> I was surprised to see Dscho advocating removing this feature altogether.
> Others proposed other command sequences which avoided :/ .
> If :/ is now going to be extended and thus perhaps more likely to
> appear in scripts,
> is now the time to change it to ? which has no other special meaning to git?

There are number of problems with ":/" notation, but my biggest gripe is that it is only slightly better than "give back a random commit". You cannot even tell it to "dig from these branch tips, look for the first one that talks about this text".

As Dscho mentioned, --grep works much better and instead of saying:

    $ git diff ':/send-email' HEAD

we can say:

    $ git diff \
      $(git log --pretty=format:%H -1 --grep=send-email master next) HEAD

The error behaviour is somewhat different between the two, though. When you misspell what to grep, the command substitution will give empty and you would get an unexpected result. Being built-in, ':/' syntax can say "I do not find anything that match" fairly easily, and the command substitution version has to say something ugly like:

    $ git diff \
        $(
            x=$(git log --pretty=format:%H -1 --grep=send-email master next)
            case "$x" in
            ('') echo 0000000000000000000000000000000000000000 ;;
            (?) echo $x ;; esac
        ) HEAD

to get a similar effect.

But the point is that you can extend it easily with the :path suffix if you wanted to:

    $ git show \
        $(git log --pretty=format:%H -1 --grep=send-email):git-send-email.perl

You can even alias "log --pretty=format:%H -1" if you wanted to, and use revision limiter other than --grep, like this:

    (in .git/config)

	[alias]
        	pick = log --pretty=format:%H -1

    $ git diff --stat $(git pick -- Documentation)^
    $ git blame $(git pick pu -- remote.c) remote.c

So in short, ':/' is limited (cannot be suffixed with :path, cannot be told to dig down from named revs, etc.) but you can do what ':/' cannot do fairly easily with command substitution.

However, $(git pick --all --grep=something), without suffixed modifiers such as ~$N and :$path, may still be common enough that it might deserve a short-hand ':/' (and that is why we have it).

If people do not find that short-hand useful, I am not strongly opposed to the idea of dropping it. I personally find the notation not very useful cute hack anyway ;-).