tests/test-wireproto-command-listkeys.t

copies: filter out copies from non-existent source later in _chain()

_changesetforwardcopies() repeatedly calls _chain(). That is very
expensive because _chain() does lookups in the manifest. I hope to
split up the function in two parts: 1) simple chaining, not
considering end points, and 2) filter out files that don't exist in
the end points (and ping-pong copies/renames).

This patches gets us closer to that by moving the check for
non-existent source later in the function. Now there are no more
checks for "src" and "dst" in the first loop; all the filtering of
invalid copies is done in the second loop. The code also looks much
more consistent now.

No measureable impact on `hg debugpathcopies 4.0 4.8`. That shouldn't
be surprising since the only case we're doing more checks now is in
case of chained copies/renames, which are quire rare in practice.

Differential Revision: https://phab.mercurial-scm.org/D6277

  $ . $TESTDIR/wireprotohelpers.sh

  $ hg init server
  $ enablehttpv2 server
  $ cd server
  $ hg debugdrawdag << EOF
  > C D
  > |/
  > B
  > |
  > A
  > EOF

  $ hg phase --public -r C
  $ hg book -r C @

  $ hg log -T '{rev}:{node} {desc}\n'
  3:be0ef73c17ade3fc89dc41701eb9fc3a91b58282 D
  2:26805aba1e600a82e93661149f2313866a221a7b C
  1:112478962961147124edd43549aedd1a335e44bf B
  0:426bada5c67598ca65036d57d9e4b64b0c1ce7a0 A

  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
  $ cat hg.pid > $DAEMON_PIDS

Request for namespaces works

  $ sendhttpv2peer << EOF
  > command listkeys
  >     namespace namespaces
  > EOF
  creating http peer for wire protocol version 2
  sending listkeys command
  response: {
    b'bookmarks': b'',
    b'namespaces': b'',
    b'phases': b''
  }

Request for phases works

  $ sendhttpv2peer << EOF
  > command listkeys
  >     namespace phases
  > EOF
  creating http peer for wire protocol version 2
  sending listkeys command
  response: {
    b'be0ef73c17ade3fc89dc41701eb9fc3a91b58282': b'1',
    b'publishing': b'True'
  }

Request for bookmarks works

  $ sendhttpv2peer << EOF
  > command listkeys
  >     namespace bookmarks
  > EOF
  creating http peer for wire protocol version 2
  sending listkeys command
  response: {
    b'@': b'26805aba1e600a82e93661149f2313866a221a7b'
  }

  $ cat error.log