Re: Splitting a rev list into 2 sets

From: Thomas Rast <trast@inf.ethz.ch>
Date: Jun 20, 2013, 13:20 UTC
Message-ID: <8761x87wc8.fsf@linux-k42r.v.cablecom.net>
In-Reply-To: <CAC9WiBi-E+LN4hKGeu0mG7ihJWCaTg-W1Dx_PWmX_vsx-uLOaw@mail.gmail.com>

Francis Moreau <francis.moro@gmail.com> writes:

Show 24 quoted lines

> Hello,
>
> I'd like to write a script that would parse commits in one of my repo.
> Ideally this script should accept any revision ranges that
> git-rev-list would accept.
>
> This script should consider commits in master differently than the
> ones in others branches.
>
> To get the commit set which can't be reached by master (ie commits
> which are specific to branches other than master) I would do:
>
>   # "$@" is the range spec passed to the script
>   git rev-list "$@" ^master | check_other_commit
>
> But I don't know if it's possible to use a different git-rev-list
> command to get the rest of the commits, ie the ones that are reachable
> by the specified range and master.
>
> One way to do that is to record the first commit set got by the first
> rev-list command and check that the ones returned by "git rev-list $@"
> are not in the record.
>
> But I'm wondering if someone can see another solution more elegant ?

I think there's a cute way.  Suppose your arguments are of the form

  p1 p2 ... --not n1 n2 ...

that is each pX is positive, and each nX is negative. Then as you observed, building the difference with master is easy: just add it to the negative args.

Intersecting with master is harder, because you don't know what parts of it (if any) are in the range. But the --boundary option can help: these are the commits where the positive and negative ranges "first" met, and prevented the walk from continuing.

So the part of master reachable from p1, p2, etc. is exactly the set of boundary commits of 'p1 p2 ... ^master'. And on top of that, excluding the parts reachable from the n's is easy. So you can do:

  positive=$(git rev-parse "$@" | grep -v '^\^')
  negative=$(git rev-parse "$@" | grep '^\^')
  boundary=$(git rev-list --boundary $positive ^master | sed -n 's/^-//p')
  # the intersection is
  git rev-list $boundary $negative

I haven't tested it much, however.

-- 
Thomas Rast
trast@{inf,student}.ethz.ch