narrow: import experimental extension from narrowhg revision cb51d673e9c5 Adjustments: * renamed src to hgext/narrow * marked extension experimental * added correct copyright header where it was missing * updated hgrc extension enable line in library.sh * renamed library.sh to narrow-library.sh * dropped all files from repo root as they're not interesting * dropped test-pyflakes.t, test-check-code.t and test-check-py3-compat.t * renamed remaining tests to all be test-narrow-* when they didn't already * fixed test-narrow-expanddirstate.t to refer to narrow and not narrowhg * fixed tests that wanted `update -C .` instead of `merge --abort` * corrected a two-space indent in narrowspec.py * added a missing _() in narrowcommands.py * fixed imports to pass the import checker * narrow only adds its --include and --exclude to clone if sparse isn't enabled to avoid breaking test-duplicateoptions.py. This is a kludge, and we'll need to come up with a better solution in the future. These were more or less the minimum to import something that would pass tests and not create a bunch of files we'll never use. Changes I intend to make as followups: * rework the test-narrow-*-tree.t tests to use the new testcases functionality in run-tests.py * remove lots of monkeypatches of core things Differential Revision: https://phab.mercurial-scm.org/D1974

Make a narrow clone then archive it
  $ . "$TESTDIR/narrow-library.sh"

  $ hg init master
  $ cd master

  $ for x in `$TESTDIR/seq.py 3`; do
  >   echo $x > "f$x"
  >   hg add "f$x"
  >   hg commit -m "Add $x"
  > done
  $ cat >> .hg/hgrc << EOF
  > [narrowhgacl]
  > default.includes=f1 f2
  > EOF
  $ hg serve -a localhost -p $HGPORT1 -d --pid-file=hg.pid
  $ cat hg.pid >> "$DAEMON_PIDS"

  $ cd ..
  $ hg clone http://localhost:$HGPORT1 narrowclone1
  requesting all changes
  adding changesets
  adding manifests
  adding file changes
  added 3 changesets with 2 changes to 2 files
  new changesets * (glob)
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved

The clone directory should only contain f1 and f2
  $ ls -1 narrowclone1 | sort
  f1
  f2

Requirements should contain narrowhg
  $ cat narrowclone1/.hg/requires | grep narrowhg
  narrowhg

NarrowHG should track f1 and f2
  $ hg -R narrowclone1 tracked
  I path:f1
  I path:f2