Re: [wishlist] git branch -d -r remotename

From: Junio C Hamano <junkio@cox.net>
Date: Mar 19, 2007, 06:40 UTC
Message-ID: <7v4pohka7g.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <7v8xdtkb7p.fsf@assigned-by-dhcp.cox.net>

Junio C Hamano <junkio@cox.net> writes:

Show 17 quoted lines

> The standard way to check if commit A is included in (i.e. is an
> ancestor of) commit B, without traversing the ancestry chain of
> B all the way down to the root commit, is to run:
>
> 	git merge-base --all A B
>
> and see if A appears in its output (if so, then A is an ancestor
> of B, otherwise it is not).  This is a pair-wise check, and for
> your purpose the check would become N*M operation (Yuck).
>
> The same check can be done in parallel with:
>
> 	git show-branch --independent A B C D...
>
> whose output would include A if the commit is not included in
> any of the other commits B C D...  This parallel traversal has a
> limit --- you can only check 25 branches at a time.

Well, I was silly. If you want to see if A is an ancestor of any of B C D..., the standard and most efficient way to do so is with rev-list.

	git rev-list A --not B C D...

will show _nothing_ only when A is an ancestor of one (or more) of B C D..., so you invoke it and upon getting the first line of output you declare A cannot be removed without reading the remainder of the output.

show-branch --independent is an overkill for your purpose as it does not treat A any more special from others (iow, it checks if B is contained in A C D..., C is contained in A B D... all in parallel), and you are not interested in finding out how remote refs are related with each other.