Re: Fwd: [RFC/FR] Should "git checkout (-B|-b) branch master...branch" work?

On Fri, Dec 21, 2012 at 11:43 AM, Michael Haggerty [off-list ref] wrote:

On 12/21/2012 06:12 PM, Junio C Hamano wrote:

quoted

"diff" is always about two endpoints, not the path that connects
these two endpoints (aka "range"), and when you want to "diff"
between two commits, you say "diff A B".  "A..B" happens to be
accepted as such only by accident (e.g. the old command line parser
did not have a reliable way to tell "^A B" and "A..B" apart), not by
design.

Off topic: I also find it hard to wrap my head around what diffing
against a negative revision would mean. Looking at the result of
running it, it seems to be the same as diffing against a positive one.

quoted

    side note: incidentally, now we have rev_cmdline_info support,
    we could start deprecating "diff A..B" syntax.

I often find myself using "git diff A..B" syntax when using the command
line history because the previous command used "A..B"; e.g.,

    git log A..B
    git diff A..B

The problem with this, to me, if it wasn't clear, is that "git log
A..B" shows you is new _since B branched off from A_, while "git diff
A..B" shows you what has changed _between A and B_.

quoted

Actually, in many places where the command line parser knows it
wants a single point, and never a range, we should be able to apply
the "A...B as a notation to specify a single point" rule.

Of course you could come up with a symbol other than "..." for that
purpose, and migrate the current "git checkout A...B" special case
to use that other symbol, but that would be more work and also you
would need to retrain existing users.

OTOH making A...B sometimes mean a range and sometimes a merge-base
(depending on context) adds a confusing non-uniformity, and also has the
disadvantage of making merge-base shorthand unavailable in contexts that
allow a range.

And making it unavailable in contexts where the command was not
specifically implemented to support it. I'm sure there are many
scripts out there that use "git ... $(git merge-base A B) ..." that
could be simplified if rev-parse could resolve a merge base.

OTOOH git already has so many notations that can be used on the command
line; inventing yet another one would make it that much more overwhelming.

Agreed.