Re: Splitting a rev list into 2 sets

Francis Moreau [off-list ref] writes:

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

Hi,

On Thu, Jun 20, 2013 at 3:20 PM, Thomas Rast [off-list ref] wrote:

Francis Moreau [off-list ref] writes:

quoted

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

Really nice !

  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.

I didn't know that git-rev-parse could be used to transform any range
specification into that form (p1 p2 .. -not n1 n2..)

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:

Really clever.

  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 think there's a minor issue here, when boundary is empty. Please
correct me if I'm wrong but I think it can only happen if positive is
simply master or a subset of master. In that case I think the solution
is just make boundary equal to positive:

     # the intersection is
     git rev-list ${boundary:-$positive} $negative

Now I'm going to see if that solution is faster than the initial one.

Great Thanks
--
Francis