contrib/packagelib.sh

revset: add depth limit to descendants() (issue5374)

This is naive implementation using two-pass scanning. Tracking descendants
isn't an easy problem if both start and stop depths are specified. It's
impractical to remember all possible depths of each node while scanning from
roots to descendants because the number of depths explodes. Instead, we could
cache (min, max) depths as a good approximation and track ancestors back when
needed, but that's likely to have off-by-one bug.

Since this implementation appears not significantly slower, and is quite
straightforward, I think it's good enough for practical use cases. The time
and space complexity is O(n) ish.

  revisions:
  0) 1-pass scanning with (min, max)-depth cache (worst-case quadratic)
  1) 2-pass scanning (this version)

  repository:
  mozilla-central

  # descendants(0) (for reference)
  *) 0.430353

  # descendants(0, depth=1000)
  0) 0.264889
  1) 0.398289

  # descendants(limit(tip:0, 1, offset=10000), depth=1000)
  0) 0.025478
  1) 0.029099

  # descendants(0, depth=2000, startdepth=1000)
  0) painfully slow (due to quadratic backtracking of ancestors)
  1) 1.531138

# Extract version number into 4 parts, some of which may be empty:
#
# version: the numeric part of the most recent tag. Will always look like 1.3.
#
# type: if an rc build, "rc", otherwise empty
#
# distance: the distance from the nearest tag, or empty if built from a tag
#
# node: the node|short hg was built from, or empty if built from a tag
gethgversion() {
    make cleanbutpackages
    make local || make local PURE=--pure
    HG="$PWD/hg"

    $HG version > /dev/null || { echo 'abort: hg version failed!'; exit 1 ; }

    hgversion=`LANGUAGE=C $HG version | sed -ne 's/.*(version \(.*\))$/\1/p'`

    if echo $hgversion | grep + > /dev/null 2>&1 ; then
        tmp=`echo $hgversion | cut -d+ -f 2`
        hgversion=`echo $hgversion | cut -d+ -f 1`
        distance=`echo $tmp | cut -d- -f 1`
        node=`echo $tmp | cut -d- -f 2`
    else
        distance=''
        node=''
    fi
    if echo $hgversion | grep -- '-' > /dev/null 2>&1; then
        version=`echo $hgversion | cut -d- -f1`
        type=`echo $hgversion | cut -d- -f2`
    else
        version=$hgversion
        type=''
    fi
}